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.
I don't believe in the Law of Attraction. There were things I wanted in my life that no amount of positive thinking was going to make it a reality for me. However, I have learned to believe in the Law of Tough Love. Life has thrown a dozen tragedies at me. I now realize that life is not about fulfilling a wish list; rather a need list. Good and bad experiences are on the horizon. How else does a person change, grow and evolve?