Failing tests puts me into homework overdrive too, to the point where I'll spend upwards of 12 hours studying on my days off from work, and 4-8 hours on work days (even though I get off work at 11pm). So you're not alone in this. It is a vicious cycle, and if you're bipolar like me apparently you'll end up manic because that's what always happens to me when I go study crazy and lose sleep. It sucks to be on edge all the time, not knowing whether you'll pass or fail a class. I'm there right now, and I was last term too, even though I'm a straight A student. I'm just having bad adhd issues that my pdoc refuses to treat.