The Savior counseled, "Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you." He set the perfect example of forgiveness when He was on the cross. Referring to the Roman soldiers who had crucified Him, He prayed, "Father, forgive them; for they know not what they do."
I appreciate these sage words from Henry Wadsworth Longfellow, "If we could read the secret history of our enemies we should find in each man's life sorrow and suffering enough to disarm all hostility." In other words, if we could see each other the way that God sees us, we would be much more willing to cut each other some slack!
I believe that forgiving others is an important requirement for happiness. Need more advice on just HOW to forgive others? I found some practical advice here.
And remember: "To err is human, to forgive divine.” -Alexander Pope