Rambam, Mishneh Torah, Hilchos Deios, Chapter 3: Not to be an ascetic and for all one’s deeds to be for the sake of heaven

Chapter 3: Not to be an ascetic and for all one’s deeds to be for the sake of heaven

A person should not be radical and say that since jealousy lust and honor is evil therefore he will separate himself from characteristics to a radical extreme to the point that he doesn’t eat meat or drink wine and does not get married and lives in a rundown home and wears raggedy clothing.
In truth, this too is a very bad path to follow and a person who does so is considered a sinner, as the sages teach us regarding a Nazir that he is considered to have sinned for swearing to abstain from wine, and all the more so for people who abstain from everything else.
A person should only abstain from those things that the Torah itself prohibited.
Fasting: Accordingly, those who fast habitually are not following a good path and indeed the sages prohibited one from mortifying one’s body through fasting.
On this King Solomon instructed us that one should not be overly righteous.

A person is required to perform all of his actions for the sake of heaven, for the sake of becoming close to G-d. This includes his sitting, standing, and speaking, that they should all be done for the sake of G-d. The following are some examples:
Business dealings: A person should not engage in business simply for the sake of gathering wealth, and rather he should do so for the sake of providing his body with food and drink and shelter and to help him get married and supportive family.
Eating and drinking and Marital intimacy: A person’s eating and drinking and marital intimacy should not be simply for the sake of pleasure to the point that he only eats and drinks that which tastes good, and only has intimacy for the pleasure. Rather, a person should drink for the sake of benefiting his body, and should only eat healthy foods whether bitter or sweet, and not eat like a dog and donkey without discretion all foods that tastes good even if they are not healthy.
One who is hot-blooded: For example, a person who is hot-blooded should not eat meat and honey or drink wine, and should drink root juice even though it is better.
Marital intimacy: Likewise, he should only have marital intimacy when he needs to really seed for health purposes or for purposes of procreation, and not simply whenever he has a lust for it.

Even one who follows health directives to the full he should not do so simply so we have a healthy body and have productive children who assist him but rather should do so in order so he has the strength to serve G-d as it is not possible to study and comprehend Torah in a state of hunger and illness and pain.
Having children for the sake of heaven: Likewise, his intent to have children should not be simply for the purpose of serving him, but so that he be a Torah scholar and great man amongst Israel.
A person who follows the above path ends up serving G-d throughout all the days of his life, including during his times of business and intimacy and sleep, as all of his actions are permeated with the goal of serving G-d.
Sleep: A person who sleeps for the sake of being reenergized so he can serve G-d also ends up serving G-d during his sleep.
On this the sages state that all of one’s actions should be for the sake of heaven, and on this King Solomon proclaimed that one should know G-d in all of his ways.