Sometimes I get burnt out. Who doesn't? I'm very sensitive to it though because I know it can be devastating to a startup, especially a single founder startup.
Over the past several years I've learned that a burnout antidote, at least for myself, is rapid prototyping of something brand new. It could be a skunk works project for the startup, but more often than not, it is something just off the wall.
Actually, it doesn't even have to be software related at all. Recently I cleaned out and organized our basement.
I didn't think too much about this process (except for that it works for me) until the other day. Upon reflection, I think why it works is the satisfaction of pushing a minimum viable product out the door.
It's fun and you're left with a great sense of accomplishment. And since it isn't your main thing (startup), you don't feel you have push past that mirage 80% completion and spend the rest of your life on the final 20%.
That's why working on a project related to your startup often doesn't work for this solution. First off, it can't be incremental because then you don't get the satisfaction. But even if it is something brand new, you could feel compelled to keep working on it, especially if it hits users. Now that may not be a bad thing at all; it just may not help with burnout.
The other thing I've learned to stave off burnout as much as possible is to get a lot of user feedback. Ideas and suggestions from real users really motivates me.
Update: also some good comments on HN.