Can you tell me how to forget painful memories?

May not be possible: Painful memories are usually not easily forgettable. Learning to live with them, to put them in perspective, to forgive yourself and others and to seek spiritual solace are all things to try. Memorials, tributes, making amends, volunteering, scrapbooking, journaling, meditation and prayer can be beneficial. A good counselor and a good friend always help too.