"Look out for one another's interests, not just our own." —Philippians 2:4 (GNT)
Proverbs 17:9 says, "Love forgets mistakes."
It's not that you are blind to someone else's faults; rather, you choose to overlook them. Great friends are good forgetters. They forget the bad stuff intentionally. They don't rub it in, they rub it out.