Luke 12:48 "...to whom much has been given, from him shall much be required."
Forgiveness is part of the 'much that has been given', and to forgive others is part of the 'much that will be required'. Failure to forgive others, or yourself, is a dangerous road.
First, anger is connected to offending actions. After the anger has been retained for a while, it leads to personal choices that bring new and painful consequences that are unrelated to the initial offense or offender(s). Finally, retained anger turns a person into an unhappy, self-identified victim that blames anyone and everyone (except self) for every real or imagined grievance. According to the angry one, he or she is worse off than everyone else, and nothing is his or her fault.
The dangerous road results from grossly undervaluing God's forgiveness and a vastly overvalued sense of personal worth apart from God. That wicked valuation is a greater offense to God than any offending action(s) the angry one had initially suffered.
To forgive is to let go of anger in the realization that God paid as much for my sins as for the sins of others. You and I are guilty of all possible wrongs against God in either thought, word, or deed. Having been forgiven in Christ, with others, "Be angry, and do not sin: do not let the sun go down on your wrath." (Ephesians 4:26).
Angry souls vent discontented passions and like wind on a fire rage more and more.
