When you forgive, trust and believe the best even in those who have shown you their worst. If you continue to revisit and relive past hurts you will never heal.
The entire object of true friendship/relationships is to make people not merely do or say the right thing, but to enjoy saying and doing the right things; not merely to like, but to enjoy being admired, and not merely to love, but to love unconditionally and all their flaws.