I started programming in 1980, and I having just as much fun now as I did then. I literally cannot wait to sit down at my IDE and start writing.
But that was not always true. When I worked for a larger company, even some startups, it was not always fun. There's something about having full control over my environment that makes the work feel like play.
If you feel like programming isn't fun anymore, maybe switching to a consulting gig will help. It will give you the independence and control that you might be craving.