The dangers and effects of getting angry:

During a state of anger one’s Neshama [i.e. G-dly soul] leaves him [and a soul of Kelipa enters into him[1]].[2] For this reason, the Sages commanded one to distance himself completely from anger, to the point that he does not feel at all any effect from the words of those who anger him.[3] [One who is angry loses his wisdom[4] and forgets his Torah learning.[5] If he was destined in Heaven to become a leader, he will be demoted from his position.[6] Anger effects and blemishes one’s entire soul, unlike other sins which only blemish one particular limb.[7] Hashem loves those who do not get angry.[8] Anger causes the body to become overheated which can lead to fever.[9] Anger enters a person into danger and can lead to gout attacks.[10]]

Mother’s anger: Mothers must especially be careful to abstain from getting angry, as Chazal[11] state that when a woman is angry, her anger destroys the home.

Not to look at the face of a person when angry:[12] Its forbidden to look at the face of a person while he is angry.

Erev Shabbos anger:[13] It is brought in the name of Rav Ahron of Karlin, that getting angry on Erev Shabbos while dealing with the Shabbos preparations, effects the blessing that the guarding of Shabbos benefits oneself and his family.

Avoiding anger on Rosh Hashanah:[14] One must be very careful not to get angry on Rosh Hashanah, as besides for the great sin of anger, doing so on Rosh Hashanah is a bad omen for the coming year.

Not to eat when angry, stressed, or in fear:[15] One must beware not to eat when he is in a state of anger or fear or stress, and is only to eat when he’s in a state of balanced happiness.

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[1] Arizal in Shaar Ruach Hakodesh 2:6; Kaf Hachaim 170:30

[2] Admur 156:3; Zohar 2 Tetzaveh p. 182; See Shlah Shaar Haosiyos Reish; Shaar Ruach Hakodesh 2:6 p. 9; Kaf Hachaim 170:30

The reason: The verse [Iyov 18:4] states “Toref Nafsho Beapo.” [Admur ibid] From here we learn that one chases away his soul with his anger.

[3] Admur ibid; Rambam ibid

[4] Pesachim 113b

[5] Nedarim 22b; Shaar Ruach Hakodesh in name of Arizal that the main source of forgetfulness is anger

[6] Pesachim 66b

[7] Arizal in Shaar Ruach Hakodesh 2:6; Kaf Hachaim 170:30

[8] Pesachim 113b

[9] Kitzur SHU”A 32:22

[10] Sefer Zechira; Sefer Shemiras Haguf Vihanefesh [Lerner] 253

[11] Sotah 3b

[12] Reishis Chochmah Shaar Hanava 2 based on Zohar

[13] Piskeiy Teshuvos 156 footnote 43

[14] Ben Ish Chai Parshas Nitzavim 6; Kaf Hachaim 583:20; Chayeh Adam 139:6; M”B 583:5

[15] Kitzur SHU”A 32:22