Mark 11:25-26 King James Version (KJV)
25 And when ye stand praying, forgive, if ye have ought against any: that your Father also which is in heaven may forgive you your trespasses.
26 But if ye do not forgive, neither will your Father which is in heaven forgive your trespasses.
I am not half the expert that I should be in forgiveness, and I know that there are times when forgiveness seems impossible. Not only has God commanded it, but study after study has proven forgiveness is healthier than holding grudges. Being angry makes you sick and unhappy. If you can’t forgive, pray for that person, and ask God to help you forgive.
I know some of you are saying “But you don’t know what person X put me through!” Not precisely, but I do know what it is like when even the court system says you have a right to hold a grudge. It isn’t easy, and it may take some work, but it is essential.