Forget what hurt you in the past, but never forget what it taught you. However, if it taught you to hold onto grudges, seek revenge, not forgive or show compassion, to categorize people as good or bad, to distrust and be guarded with your feelings then you didn’t learn a thing. God doesn’t bring you lessons to close your heart. He brings you lessons to open it, by developing compassion, learning to listen, seeking to understand instead of speculating, practicing empathy and developing conflict resolution through communication. If he brought you perfect people, how would you ever learn to spiritually evolve?