I've only recently come out of my burnout, despite it happening years ago. It sucks. It sucks bad. But looking back, I can see many of the causes crystal clearly, that weren't so apparent at the time. Here's a list:
1. Think about your project and only the project
Let's face it. Business wants you to make the best product you can "for our customers". You put off fun features for the sake of hitting a deadline. You plan and analyze and break a project into sets of deliverables that then must be coded by a monkey (you). You demo it, gather feedback, iterate. All without thinking anything for yourself.
Read more at Josh Braegger's blog.