How can I gauge expectations better?

I have a nice problem but it's making me miserable.

My background is in visual communication and I'm used to getting regular feedback as well as seeing what my classmates are up to. Also, the grades we would get back then didn't really matter but the quality of the work was what would land us a job later so I'm always concerned with the quality of what I'm doing. Also, this sometimes makes me feel like I'm starting with a handicap as I'm not used to writing papers and English is not my first language.

Ever since I joined a Master's program in a different field, I can't seem to set reasonable expectations for myself (or align my expectations to the ones for the course). As I work on a project, I keep finding holes and making it better until I'm satisfied. Since there is little feedback and that I don't know what my classmates are doing, I just do my best or as close as I'm able to. The nice part is that sometimes the work ends up having potential for publication, I get a nice GPA and the esteem of my teachers. The not-so-good part is that I just don't have a life until school is over and my stress is really ramping up. The obvious solution would be to not try so hard but that seems like a waste of an education...

Any advice?