I'd recommend the book "The Truth About Burnout" [0]. It talks about 6 sources of burnout: work overload, lack of control, insufficient reward, breakdown of community, absence of fairness and conflicting values.
For a long time I had burnout (or only a beginning). After a while, I suspected I might be burned out and it might be because of hard work, I work part-time and go to school too. It don't think it helped now that summer has come and I don't go to school, so I read the book. I think it's because lack of control, absence of fairness, conflicting values and insufficient reward. Note that it doesn't have to be true, it's enough for you to feel unpaid, that you don't have control, etc.
The way ruby uses instance_eval. I didn't pay attention at first, I just enjoyed the beautiful interfaces. But when I saw how they use instance_eval behind the scene and how simple is, I was in awe.