The trick to avoiding complete burnout is easy. First - don't care at all about your job. Remember that all corporations are by definition psychopaths and they will treat you accordingly. Second - never do more then 35% of the work you are capable of doing in a day. Third - if you find yourself getting stressed out tell yourself repeatedly "It's only a stupid job. There is no point in stressing about it."
I'm a big fan of three-hour-per-day planning. "Metered work" (what your boss expects of you) should be limited to a 3-hour block, preferably a contiguous one. After that, find a way to sneak time into things that build your career. Don't mix the two. (You'll either cut the self-directed stuff and burn out, or give your job responsibilities the shaft and at zero, you might actually get fired.) When you need to spike, turn that 3-hour dedication to 4 or 5 or 6 for a little while. The nice thing about the 3-hour plan is that it accounts for slack, because things always take longer than they should.
It takes your boss 15 minutes per week (on average) to tell you what to do. If you do 15 hours of metered work, you're giving him 60:1 leverage. That's enough not to get you fired.
The trick to becoming awesome, I think, is to take that 25 hours of "working time" per week that most people spend on Reddit or Farmville or non-work IMing and turn it into Coursera or open source time (don't ever use it to write code you'll need for a side project; legal issues make it not worth it). It's not easy, though, because it's much harder to hide it when you're studying machine learning at 2:30 in the afternoon.