Reconciliation Begins With Genuine Repentance

Forgiveness and reconciliation are two different things. Forgiveness can happen in a moment, but reconciliation is a process—a process that begins with repentance.

Genuine repentance accepts full responsibility for your actions and welcomes accountability. When you repent, you'll stop your sinful behavior without downplaying or dismissing it. You drop your defensive attitude and don’t resent the doubts of others about your sincerity. And you’ll make restitution where necessary. 

There cannot be genuine reconciliation without genuine repentance. But letting time pass without genuine repentance makes reconciliation more difficult. Which is why Jesus insisted on dealing with it right away:

Therefore if you bring your gift to the altar, and there remember that your brother has something against you, leave your gift there before the altar, and go your way. First, be reconciled to your brother, and then come and offer your gift. 
–Matthew 5:23-24