This is what I like about coding. I enjoy trying to solve those small puzzles that make up a full application. The problem sometimes is that the application gets so big and the solutions take too long that it becomes a grind.

I find that when I reach that point, it helps to take a break, look at the problem with a fresh mind, and try to break down the solution into smaller pieces. At that level, some parts become interesting and fun again, even though others might not be. At least you have fun in some of the parts, instead of feeling the grind of the entire thing.