Anger and Hostility
Anger is rooted in disrespect—and disrespect is not okay. The Bible tells us to be angry [when we are disrespected] while warning us to not sin during the process (Eph. 4:26).
Healthy anger confronts your offender with what belongs to them, i.e. their responsibility for disrespecting you.
But if you keep anger to yourself, you sin, 1) against the other person by allowing them to be irresponsible with their offense of you, and 2) you sin against yourself by keeping what belongs to another inside yourself, i.e. you own their disrespect as if it is true.
Now, you are without self-respect.
Failure to respect yourself is an identity problem that began with a performance shortfall. The only resolution is to change a performance that isn’t yours to begin with.
Good luck with that.
Now you have frustrated internalized anger that festers and abscesses. That’s the definition of hostility and you did it to yourself by holding onto something that didn’t belong to you. In so doing, you compromise your self-respect.
This is sin because you discount the respect God declared is true of you.
To read more on this theme, I offer this link.