Forgiveness is the key to faith in God.
Mark 11:20–25 (CEB): Early in the morning, as Jesus and his disciples were walking along, they saw the fig tree withered from the root up. 21 Peter remembered and said to Jesus, “Rabbi, look how the fig tree you cursed has dried up.” 
22 Jesus responded to them, “Have faith in God! 23 I assure you that whoever says to this mountain, ‘Be lifted up and thrown into the sea’—and doesn’t waver but believes that what is said will really happen—it will happen. 24 Therefore I say to you, whatever you pray and ask for, believe that you will receive it, and it will be so for you. 25 And whenever you stand up to pray, if you have something against anyone, forgive so that your Father in heaven may forgive you your wrongdoings.”

This is interesting, if I want God to answer my prayers and if I want to receive things from God, then I need to offer forgiveness to receive forgiveness. I like holding things over people’s heads, I’m that Cardinal fan who still holds on to the angst of the bad call in the ‘85 World Series. I’m that Bears fan who can’t get past the double doink and I’m that crazy Illini fan that can’t get over Bruce Pearl ratting on our program and their recruiting practices. Some of you have no idea what I’m talking about, but that’s what unforgiveness is, hanging on to hurts that no one cares about anymore and you can’t change the outcome by holding on to them. Jesus is teaching me to let go of those hurts so that God can answer my prayers and give me true life. Sometimes, I don’t even realize that I’m hanging on to unforgiveness until something makes me remember and I have to let it go and ask for forgiveness as I am forgiving.