I've been meditating more lately and I want to be able to let go of something bothering me. For context it involves a friend of mine. We were best friends but the friendship has pretty much ended. When he got in a relationship, he pretty much distanced himself. It's frustrating for me as I tried to hold onto the friendship but he's ignorant to the situation and often times mocks me in some ways. We still see each other occasionally through other people but that's the context of our relationship now.

I often deal with frustration, anger, and the need to get him back in some ways for hurting me. Plus I miss the frienship I don't think I'll ever get back. I can't hold onto this anymore. What kind of mindfulness and meditation techniques should I do to let go?