It might be good to give the NASB translation here.
(Proverbs 29:11 NASB) A fool always loses his temper, But a wise man holds it back.
A “fool” (3684) and a “wise man” (2450). Both experience inflammatory events. Both are angry. What is the difference? It is not anger, but self control. Both have a “mind" (temper NASB) (7307). One gives in, one resists.
The sin in not anger. We sometimes get this wrong. God felt anger. I believe when Jesus cleansed the temple He was angry. What could be more clear than this statement:
(Ephesians 4:26 KJV) Be ye angry, and sin not: let not the sun go down upon your wrath:
The sin is in losing your temper, in letting your emotions rule your roost. It is possible to control any strong emotion, to change any entrenched habit, to sanctify any prejudice. To paraphrase Tigger, “That is what Holy Spirits do best.” Here the example is anger but the same applies to any excess in our lives from lust to gluttony.
So? Don’t let “losing your temper” be an excuse to give in to sin. Repent of past sin. Make restitution if the Spirit convinces you it is necessary. Allow Him to do His work in you and allow Him to give you the control you need.