Sometimes you get an idea that you really like for a game, and you feel so excited about it that you spend every waking moment thinking about it and eagerly awaiting the opportunity to just let all the ideas out so you can get to work designing it. Time passes, and your excitement continues as you work on your game on a fairly regular schedule. Eventually, you get to the point where you've done a fair amount of work, but either you're just not as excited about it, or you've gotten sick of the sight of the same thing over and over. This is a crucial period, as it can easily lead to you putting your game on the back burner, or worse still, completely abandoning it. In times like these, it's time for what I like to call a "game sorbet."
As the name implies, this is a smaller, way less ambitious project intended as a break, or palate cleanser. The idea is not to lose momentum on your big project while still having something fresh to work on. It can be something as simple as a one room joke game, or something with a mini story told in 3 or 4 rooms. It's important, however, not to get too ambitious, or you'll end up right back where you started. Ideally, your sorbet game won't take more than a week or two to finish. By the time you're done with it, hopefully you'll be looking forward to returning to your main project.
I've hit that spot in A Golden Wake, and just yesterday I participated in a 4 hour game jam where I and a fellow AGSer created a silly joke game called Monty Python's Makeout Mansion. It was a lot of fun to work on, and a welcome break from AGW. Currently, I've been drawing a background and sprite for another game which I plan on spending a few days on as another distraction.
The thing to remember also is not to go overboard with sorbet games. You don't want to find yourself with 6 games in production in addition to your main one. If you make 2 or 3 sorbet games and still find you're not excited about going back to your main project, maybe it's time to step away from making games and do something else. Read a book or go for a walk or take lots of showers. At some point, hopefully some creative spark will enter your mind and you'll think of something new or a different approach to a problem you were having in your main game that will make you want to run back to it and work on it again.