How do we forgive when we don't feel like forgiving? 2 Chronicles 7 is helpful as God responds to Solomon's prayer from chapter 6. God will speak about forgiveness but before he does, he sets out the foundation of forgiveness.
2 Chronicles 7.12-13 read: the Lord appeared to him at night and said: I have heard your prayer and have chosen this place for myself as a temple for sacrifices. When I shut up the heavens so that there is no rain, or command locusts to devour the land or send a plague among my people, ...
Why did God not simply begin with the words, "I will forgive when you humble yourself before me"? Because God is teaching his people that before forgiveness takes place, one must understand grace. God speaks to Solomon expressing that He will hear but it is an ear given to sinners who deserve punishment. God knows that the people of Israel will sin but he rsponds with grace as he will hear and forgive.
So, what happens when you don't feel like forgiving? God does not simply say "forgive". Instead, he teaches about grace and found in the realm of grace is the strength to forgive.
Forgiveness is not based on feeling or strictly speaking, raw obedience. It is built upon the foundation of knowing the amazing and abounding grace of God in our lives.