I guess the larger problem is that I never feel like I'm on equal footing with the people I work for - theoretically we have the same amount of power, I could refuse to do the work or they could refuse to accept the work that I turn in, but it almost always feels like I need the work more than they do. Capitalism!
I think it's deeper and darker than that, I'd love to say that it's exclusively because I feel bad turning in inadequate work but there's definitely a part of me that is paralyzed by obligation, and another part that is extremely put off by the idea of "appeasing," so to speak, some sort of authority figure I have no loyalty to (like a client or a professor). But it's often even worse if I'm putting off work for people I respect. Life is hard~