Let's Not Die With Learning!
First off, the human body is a delicate thing. Often pathetically delicate, which rather contridicts how I treat mine. I will push my body as far as I feel it should go, while not stopping when I should. Don't do this.
Consider this a public service announcement: Over-exertion + dehydration = bad, bad things. You may not realize you're dehydrated, but if you start to get sore you should let up a bit, sit back and drink some water. The reason I bring this up is because tonight marks the third time in my life I have completely ignored such advice, and screwed up part of my body. You'll know when you finally push it to the utter limit because, like me, you'll start to piss blood.
Note: This is bad.
If that should happen, visit a doctor your first time and have yourself checked out. Otherwise, drink water. Lots of water. Cram as much down your throat as possible and you should start to be clear again. If you're peeing blood, leaving it untreated can kill you faster then you might like. No, I'm not kidding, so please remember to drink lots of water while working.
In any case, there's also the chance that I did that tonight because I ended up drinking my own blood for about twenty minutes, thanks to the most intense nosebleed I've ever had. But considering the condition my body is in (and I've only been able to walk almost properly in the last hour or so), I think it's the former. Please, listen to your body when it tells you to stop.