Advice From Byron Katie
Byron Katie has a lovely approach to forgiveness and eliminating hurt, both of which can help with being happy   Check out her work.  There is a great deal of depth to her work, here is just a small taste.

Pick a situation or a thought that is interfering with your happiness.   This could be something someone has said to you, something you believe to be true, or a judgement you have made about someone else.   Consider these questions.

1. Is it true? (Yes or no. If yes, move to 3, if no, let it go.)
2. Can you absolutely know that it's true? (Yes or no, if no, let it go.)
3. How do you react, what happens, when you believe that thought?
4. Who would you be without the thought?

I think we often hold onto thoughts or beliefs that we forget to test or that we subsequently learn are untrue, often years later. Even if they are true, often holding on to them adds no value, only pain.  What if we just let them go?  What would be different for you?  Would you be happier?