The lust involved in intimacy:
A. The History-The inception of the lust for marital relations:
In the times of Adam Harishon, prior to the sin, there was no lust involved in intimacy, and the act of intercourse between man and woman was similar to any other Mitzvah, such as putting on Tefillin, in which there is no lust contained in the limb. This is why originally the male and female genitalia did not originally need to be covered, as there was no shame regarding it. Only after the sin did the evil inclination invest itself into the limb, and thus create the great lust that we know of today.
Fixing the sin-Controlling the lust: Since Adam Harishon incorporated all the future souls, it ended up that all the souls of Israel became affected by his sin, and thus are indebted with the mission to fix the sin of Adam Harishon through controlling this lust.
Intimacy in the future:
See Sheim meshmuel
The Kelipos desire to nurture off ones physical pleasure:
The Mekubalim state that the entire desire of the Kelipos is to nurture off the actions done by a Jew. Through a Jew mentioning the name of G-d prior to doing the action, he protects and defends that the Kelipos will be unable to nurture from his actions. This especially applies towards Mitzvos that contain bodily pleasure and benefit, such as Oneg Shabbos and Yom Tov, and marital intercourse, in which the Kelipos have a great desire to nurture from, and attach to the Kedusha, as this energy is its life. It is this hungry passion of the Kelipos which seduces man to swerve from his pure intentions during marital intimacy, and perform matters that are inappropriate, in order to satiate the hunger of the Kelipos. The Tikkun for this is to state prior to starting the action that one is doing sof or the sake of G-d.
The lust of Lilis and Naamah:
One must guard that he does not become aroused and excited by foreign lusts, from Naamah, as the Zohar states that occasionally Naamah comes to the world to excite people, and the person is found in a state of lust with her, and he lusts for what he saw in his dream. Now, if he has a child from this union, this child will belong to Naamah, and when Lilis comes and sees him, she connects with this child, and is with him every Rosh Chodesh and tries to hurt him. See Chapter ?? Halacha ?? for the full details of this subject!
The Kelipa of Zenus:
The Kelipa of Zenus is the that includes all the Kelipos. Thus, Chazal state that Hashem hates Zenus more than any other sin. The reason for this is because sexual sins involves the strength of ones entire body, and causes the Kelipos to spread everywhere in the body, to all the limbs. Thus, if one does not sanctify himself during intimacy, and intends to do so to fulfill the lust, then he binds his entire soul to this Kelipa.
The greatest bodily lust is found in the male reproductive organ:
The male reproductive organ contains the greatest lust of all limbs and all worldly matters. It is for this reason that it poses the greatest challenge for man, and when man controls this limb and subjugates this lust, it shows the epitome of the advantage and difference between man versus animal. It is for this reason that we find that the lion became subdued specifically when the Or Hachaim showed him his Bris Mila, as in the control of this lust the superiority of man over animal is revealed, and causes animals to be nullified and submissive to him.
C. The reason we have a lust for intimacy is for the sake of procreation:
Every person should contemplate how the lust for marital relations was only created by G-d for the sake of procreation, and the continuity of humanity. A proof towards this can be found from the fact that as a soon as a man completes the release of his seed, his desire ceases, and he no longer lusts intimacy until he can reproduce more sperm, and have the lust once again be recreated. From the fact that man’s lust is only present when he contains seed, is the greatest proof that the entire purpose of the lust is simply to procreate. The reason that G-d created this lust is because otherwise man would not desire to be intimate with a woman and have children, and thus a passion and desire needed to be created to lead man to have intimacy and procreate. This lust is not logical, but rather a decree of G-d Who implanted it into nature.
D. The lust for intimacy is like the lust for food:
Just as there exist healthy foods and unhealthy foods, so too there exists healthy and unhealthy intimacy. When one eats healthy food there is nothing greater for his body, while when one eats unhealthy foods it ruins the body. Similarly, intimacy which takes place in a Kosher and holy method is beneficial for the body and soul, while if it takes place in a materialistic or forbidden fashion, there is nothing more damaging than it.
E. The Bris Milah is performed to diminish the lust:
The reason G-d commanded us to remove the foreskin is in order to diminish our lust for promiscuity. It is the sign that every Jew bears of G-d, his master, through which a Jew proclaims that he belongs to G-d and diminishes his desires for the sake of G-d.
F. A small limb that when satisfied becomes hungry-Overindulgence can kill intimacy and create sex addiction:
The Sages state that “There is a small limb in a man that when he satiates it, it is hungry, and when he starves it, it is satiated.” [Literally, this means that one who increases in marital relations causes himself to have an even greater lust for relations. Additionally, this means that one who increases in the marital relations he releases his energy and causes himself to feel weak in his older years. One who has relations by both night and day is considered to be over satiating himself. Some learn that the above saying of the Sages is only referring to forbidden relations; that forbidden relations never satisfy one’s lusts, while permitted relations, such as with one’s wife, does satisfy one’s lusts. This is due to another Talmudic statement that Hashem took the pleasure of Tashmish and handed it to the forbidden relations. Accordingly, it is proper not to have relations to often as doing so will satiate him and reduce the lust one has for his wife.]
How to control the lust:
To control one’s lust and passion for intimacy one needs to contemplate its origination, and how originally, in truth there was no lust involved in this limb, and the lust only came about through the sin of Adam. When one looks at this limb similar to any other limb of the body, it helps to divest it from its lust.
How can one have relations without physical lust and pleasure?
Indeed, it is not possible for a man to have an erection unless he becomes excited with lust and passion for physical pleasure, and hence the question is raised as to how one can sanctify himself during intimacy and negate any physical pleasure, and still manage to be intimate? The answer is as follows: The same way there exists a materialistic pleasure involved in intimacy, so too there exists a spiritual and holy pleasure and passion. The same way there exists a fire of passion for the material, so too there exists a fire of passion for the spiritual. Now, the intent of the Mitzvah of Kedoshim Tihyu, to sanctify oneself during intimacy, is not to negate the feeling of pleasure or passion, but rather to direct it to the proper goal and intent. Instead of one focusing on the physical, animalistic and materialistic lust for expelling of seed due to the physical beauty of a woman, one is to intend on the spiritual bonding that is taking place between the souls and bodies, and this excitement is what is meant to serve as the motivation for the intimacy and the erection. Man and woman both contain the word “אש” in their name, hinting to the Gevuros of Kedusha, the fire and passion of holiness. When the couple is intimate with soul intent to bond with each other and draw down the Divine presence into them, then they are considered to have sanctified themselves during intercourse, despite having had a most passionate and pleasurable experience. Furthermore, in truth, the existence of the physical and materialistic pleasure of intimacy derives from its counterpart root of the spiritual pleasure of intimacy, and hence when one intends on the spiritual passion, he is performing the highest form of intimacy possible. The explanation is as follows: In the world of Atzilus there exist holy Gevuros/severities. It is this level of Gevurah which creates the passion for intimacy, and of man to a woman. However, in its spiritual state, this passion is holy and focuses on the bonding of the souls, however as it descended to this physical world, it received a connotation of materialistic bodily pleasure and passion for the physical body of the woman. Thus, the job of man during intimacy is to elevate the animalistic passion and desire to its original state of spiritual passion.
The physical lusts will always be involved: Despite the beautiful philosophical approach explained above that one can focus his lust for the spiritual intimacy, it is not humanly possible to complete divest oneself of the Yetzer Hara, and lust for the animalistic and physical intimacy which desires the beauty of a woman, and the physical pleasure involved in ejaculation. Ever since the sin of Adam Harishon, this lust is embedded in the nature of man and hence at best it can be weakened and marginalized but not eradicated. It is for this reason that a man is required to immerse in a Mikveh to purify himself after intimacy, as he has become a vehicle for the Yetzer Hara during the pleasure of ejaculation.
Sanctify the erection and drop of semen:
As explained above, there exists a passion of holiness and a passion of evil during intimacy. It is the job of man to arouse his excitement for the right purposes and cleanse and purify his drop of semen as much as possible.
 Reishis Chochma 16:9 based on Rebbe Levi in name of Rebbe Shimon Ben Minasya in Midrash Raba Vayikra 20b
 Reishis Chochma 16:10
 Pela Yoeitz Erech “Dibbur”
 Reishis Chochmah 16:16 in name of Ramak in Or Hacham 96
 Acharei Mos 77a
 Reishis Chochma 16:10
 Bereishis Raba 26:5
 See Toras Menachem 1:110
 Aruch Hashulchan 240:2
 Siddur Yaavetz Seder Hanhagas Leil Shabbos
 Chasam Sofer Drashos p. 133
 Rambam in Moreh Nevuchim 3:49
 Michaber 240:1; See Elya Raba 240:5; Kaf Hachaim 240:23
 Michaber ibid; Sukkah 52b; Sanhedrin 107a
 Rashi in Sanhedrin ibid
 Rashi in Sukkah ibid; Rambam Deios 4:19; Michaber 240:14
 Tosafus in Sukkah ibid based on Sanhedrin ibid
 Keli Yakar Vayeishev 39:6
 Sanhedrin 75a
 Reishis Chochma 16:9
 Reishis Chochma 16:13-18 based on Zohar Raya Mihemna 96:34 and Or Hachama of Ramak 96
 Reishis Chochma 16:19
 Reishis Chochma 16:19