Infinity, has no beginning or end, we're in it NOW, therefore I think this is the perfect moment to focus on having fun. I've done no formal research; my conclusions are purely based on personal experience, thoughts and feelings. I definitely know what having fun feels like. I'm certain you do too.
Unfortunately, I think some of us may confine fun to only certain specified activities or days or even people. We've forgotten that it's probably available to us daily, and unfortunately some of us may have forgotten the pure, innocent, surrendering type of fun we had as kids.
Years ago, the idea of healing the inner child became very popular. Few of us have escaped the turmoils inflicted on children and may have a few scars remaining. Yet, I urge you to consider focusing on the Now since your story of pain and suffering may have changed and all you really have is the present moment. I interpret Eckhart Tolle, http://eckharttolle.com/, as proposing that we detach from our "stories" in order to fully live our current life, rather than remain attached and in effect live in the past. Yet, understandably, the process may need some attention and a little time. If such is the case, I recommend you visit http://1-healing.com/. You may find some comfort in its contents which include various healing modalities to help you let go and become grounded in this moment which is full of all kinds of possibilities - they are endless.
Years ago, as required by my social work license, I attended a training workshop on "healing the inner child". The facilitators "made" the participants engage in childhood games like, ring around the rosie and tag. I felt rather humiliated at first, but then I got the hang of it and wound up having tons of fun along with all the other inner children there. It was amazing for me to discover that I could still engage in childish things and enjoy my childish ways. Once I let down my inhibitions, I felt such freedom. I felt more genuine than I did portraying the mature, self-disciplined, self-controlled professional adult of my daily existence. I realized how much easier it became to love myself if I acknowledged that little child who still lurked somewhere inside. Healing took place. I had an open heart and a good intention. I think that's all you need.
"What!? You're going out again? Didn't you just go to a party last Saturday?" My grandmother never refrained from her inquisition type of interrogations prior to my escapes into the fun-filled world of music and dance at least once a week. It was totally beyond my comprehension why she thought there was a quota on having fun - if you had some last week, you need a rest this week. Somehow, I almost always managed to get away and join friends to listen to the top songs and practice the newest moves. That was the highlight of my week. I still feel deprived if I don't do something fun on Saturday nights. Though I am mostly confined to staying home and enjoying a good meal and a movie, I play my music loud and dance alone at any opportunity. That teenager is still active somewhere within me and although she's from the past, if I let her come out , she still knows how to have fun - and I must say - how to move.
If you need inspiration to have some fun visit http://eightprinciples.com/. This will at least propel you into the fun mindset, which has the potential to alter your life.