I lost a very close uncle, you have not lost the spark, it's grief which is a horrible state to be in I found working even harder focused my mind and it did not really matter what I did as long as I was invloved. Distraction is good but I also discovered that taking a few mins to reflect on the positive effect he had on my life actually cheered me. It's sounds harsh but I found it very easy to feel sorry for myself and it was my wife who shook me by telling me I was being selfish keeping everything to myself and that my uncle would kick me up the bum if he could see me. She also told me sharing would help, and she was right.
Keep going, focus and find someone to share positive memories with. I think of him daily and I always have a chuckle and it's a great place to be.
Good luck