The Bible has recorded a bit about forgiveness and unforgiveness. The most well-known teaching on unforgiveness is Jesus parable of the unmerciful servant.
The servant was forgiven by a king and yet he refuse to forgiven the little debt he was been owed by his fellow man.
God’s forgiveness is not based on the on our works. Forgiveness and salvation are both founded completely in God and by Jesus redeeming work on the cross.
A lot of people has ruined their life with the bitterness and forgiveness in their heart. If we don’t learn to forgive people we indirectly hand our lives over the hand of the evil doers.
When you learn to forgive, you feel a burden lifted off your shoulders and you feel free and happier.