John tells us in 1 John 1:9 "If we confess our sins, He is faithful and just to forgive us of those sins and cleanse us from all unrighteousness."
It's hard to fathom something so amazing like God's grace and mercy. It's hard because we know what it feels like to have somebody do wrong to us. And when somebody wrongs us, it's DIFFICULT to forgive them... God, on the other hand, doesn't hold grudges or give ultimatums or anything like that... He knows our hearts wants us to get back on the right path and get the sin out of our life.
We need to be practicing forgiveness in our own lives each day... In knowing that God forgives everybody for their sins and unrighteousness, we have no reason or right not to forgive those who have sinned against us. Like I said, It's difficult - but it's something that we as Christians must do. We must forgive others if we ourselves want to be forgiven.
Praise be to God for cleansing us of our sins and let us pray that He will give us the strength to forgive those who have wronged us.