Exodus 32:14 New International Version (NIV)
14 Then the Lord relented and did not bring on his people the disaster he had threatened.
God changed his behavior to remain consistent with his nature. God wanted to destroy the people, and this was consistent with his justice. Moses interceded for the people. God acted consistently with his mercy. Change your ways, and God will forgive you. God promises to forgive if you ask him and change your behavior. Repent means to change. Sin is going against God. Repent from sin and ask to be forgiven, and God promises to move your sin as far as the east if from the west. He will not hold your wrong choices against you. They are gone, and you are a fresh new person.