You know, I'm something of a failed game developer myself.
The #1 thing I learned was: Set your sights low. Lower than you think you should have to. And then lower than that. And now take that and cut it in half. Got it? Okay, now, from that, figure out what you think you could get done in 2 weeks. And now imagine that you're 2 days in and someone told you you actually only have 1 week to finish completely. Pencils down, you can never work on this again. What would you focus on?
If the design is only fun if there are heaps and heaps of content, hyper-realistic art, epic soundtrack, and intricately-tuned parameters, you're pretty much doomed to fail. It has to be fun even with one basic level, placeholder art, some sfxr audio clips, and wildly unbalanced stats.