When you are in distress and all these things have happened to you, then in later days you will return to the Lord your God and obey him. For the Lord you God is a merciful God; he will not abandon or destroy you or forget the covenant with your forefathers, which he confirmed to them by oath. Deuteronomy 4:30-31
The mercy of God is his greatest attribute. Our greatest fear when we sin is that God will act as so many people do, clucking the tongue and saying, “You expect me to forgive after you did that?” But the reality is that God really and truly does promise forgiveness of all our sins, if we will only turn to him for mercy.
People are made in the image of God, to be sure. But people are fallen too. Our failure to be merciful is not a sign that God is like us, it is a sign of how far we have fallen away from the God of mercy. So don’t let the rejection of people in the past make you fearful of seeking God’s mercy. Ask for mercy and he will surely give it.
If he can forgive those who crucified him, he can forgive any other sin for which we ask pardon and he can give us the grace to forgive those who have had no mercy on us.