One of the hardest parts of being a Christians is to forgive others who have done something against us, whether it be accidental or intentional. Forgiveness means that we never use an incident as a weapon against the person who wronged us. We will not be able to forget what someone did to us but we must be diligent in avoiding the temptation to resurrect it.

All our sins were forgiven
(Col 2:13 KJV) And you, being dead in your sins and the uncircumcision of your flesh, hath he quickened together with him, having forgiven you all trespasses;
Forgive one another
(Eph 4:32 KJV) And be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ's sake hath forgiven you.
We should be ready to forgive
(Psa 86:5 KJV) For thou, Lord, art good, and ready to forgive; and plenteous in mercy unto all them that call upon thee.
Forgive the sin debt of others
(Mat 6:12 KJV) And forgive us our debts, as we forgive our debtors.
Forgiveness is an outward sign of salvation
(Mat 6:14-15 KJV) For if ye forgive men their trespasses, your heavenly Father will also forgive you: {15} But if ye forgive not men their trespasses, neither will your Father forgive your trespasses.
Forgiveness must be open ended
(Mat 18:21 KJV) Then came Peter to him, and said, Lord, how oft shall my brother sin against me, and I forgive him? till seven times?
(Luke 17:3-4 KJV) Take heed to yourselves: If thy brother trespass against thee, rebuke him; and if he repent, forgive him. {4} And if he trespass against thee seven times in a day, and seven times in a day turn again to thee, saying, I repent; thou shalt forgive him.
Forgiveness must be sincere
(Mat 18:35 KJV) So likewise shall my heavenly Father do also unto you, if ye from your hearts forgive not every one his brother their trespasses.