Therefore, if you are offering your gift at the altar and there remember that your brother or sister has something against you, leave your gift there in front of the altar. First go and be reconciled to them; then come and offer your gift.
Matthew 5:23-24 (NIV)
Because the Bible asks us to forgive and forget, the majority of believers rely much more on this aspect to get others to forget or put aside the wrongs they have done to them. They overlook the most important aspect of forgiveness, acknowledging wrongdoing and asking for forgiveness.
What Jesus means in the verse is that if your brother can have anything against you, it is because at some point you have wronged him. What is in his heart is the harm he has suffered. He will always remember it until you do something to fix it. He will remember it.
God himself illustrates the importance of admitting sin and confessing it. 1 John 1:9 tells us, "If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness." You see, if you want others to forgive you, it's essential to admit your wrongdoing and openly apologize to them. Apologies can be seen as a kind of confession.
If you have wronged someone, don't think he/she should forgive you because you are part of the same body, rather be wise and humble, go to him/her, admit your wrong and apologize and, their heart will be released forever.