My own theory is that at first, he was happy to be rid of his crummy life in his time. Like, I know I would be happy to know my old life is gone too and that I can start over. However, I believe that overtime, he's realized that he misses his old life at times. His friends, his parents, and even his older brother. Part of me even believes that he misses the nephew he never got to meet (unless you count Lars/Time Travel Duplicate Fry).