Mike Loomis gives an eloquent explanation of how burnout happens in a blog post entitled "Why Do Young Superstars Suffer Job Burnout?":
As the workload expands, her days get longer and her performance suffers. She might get some critical feedback. It could be that the young hotshot behind her isn’t getting the opportunity to really contribute, and is unhappy. Her boss lets her know it’s her responsibility to train the new talent. Or, maybe she’s missed some deadlines and her boss is second-guessing her. There’s just too much work to do and she’s not very good at delegating. It’s a quick slide from here...
The most interesting part of this post, to me, is the dichotomy that's drawn between the academic mode and the professional.
In the academic world, you get ahead by doing. Group projects are the bane of any sensible student's existence: other people are unreliable. You get ahead by putting forth your best effort and not allowing the deficiencies of others to impact your performance.
In the professional world, a focus on doing is a great way to get burnt out and make your team to hate you. After school, you have to love group projects to get ahead.