Musar for Nedarim 43:12

Accustom yourself to always speak all of your words calmly, to every man and at every time. In doing so you will prevent your anger from flaring, which is a bad attribute in a man which may cause him to sin. And accordingly said our Rabbis, may their memories be a blessing: (Nedarim 22a) "Anyone who gets angry - all of Gehinnom holds sway over him, as it says: (Kohelet 11:10) 'And remove the anger from your heart, and take away the bad from your flesh', and 'bad' can only mean Gehinnom, as it says (Proverbs 16:4): 'And the sinner, he too, will have his day of bad'."

Anger is a bad quality and just as scurvy is a disease of the body so is anger a disease of the soul. And our sages have said : "He who loses his temper is exposed to all the torments of hell" (Nedarim 22a) as it is said : "Therefore, remove vexation from thy heart, and put away evil from thy flesh" (Eccl. 11:10), and by "evil" they mean Gehenna, as it is said : "The Lord hath made everything for His own purpose, Yes, even the wicked for the day of evil" (Prov. 16:4). And not only this but an angry man is afflicted with piles as it is said : "The Lord will give you there an anguished heart and eyes that pine, and a despondent spirit" (Deut. 28:65). What ill is it that dims the eyes and pains the soul— Surely you will say "Piles".

And Chazal have said (Pesachim 66b): "Any man that gets angry — even if greatness has been decreed for him [by Heaven], he is brought down [from that greatness]. "and Chazal have said further (Nedarim 22a): "Whoever gets angry — all kinds of Gehinnom prevail over him." The intent is that for each [kind of] sin in itself there is, in Gehinnom, a distinct punishment for that sin. And through the trait of anger a man comes to all the different kinds of sin [as is clear] to one who reflects upon the evil of that trait, to the extent that Chazal have said about him that of a certainty his sins are more abundant that his merits. This is the intent of "All kinds of Gehinnom prevail over him." Therefore, a man must remove anger from his heart and he will be saved from Gehinnom and will merit life in the world to come.