Stop working 15 hour days. That's just stupid and grossly counter-productive. Work your 8 hours, then go home and don't think about it. Your brain needs time t

Stop working 15 hour days. That's just stupid and grossly counter-productive. Work your 8 hours, then go home and don't think about it. Your brain needs time to absorb, process, and synthesize. It can't do that if you're trying to force-feed it new information faster than it can handle. Take some time to write a couple tests against the code, to make some small refactorings, etc. If you still feel overwhelmed or underwater, talk with your manager and just tell them the code is a pile of crap (if it really is). They don't want to hear it, but they might cut you some slack.