I seem to go through the same problem, if this should be considered a problem. A lot of it has to do with how mundane and repetitive my days, especially my weekends, are. I never seem to be able to do anything fun or memorable, so instead, I observe society and think a lot. It's really all I can do. The point I'm getting to is that you should probably find something you'd love to do. What are your hobbies? If you lack hobbies, try to find one. You can volunteer and/or do charity work.
But again, I don't know exactly what you're going through, so it's all on you to make yourself happy.