alarm clocks turning off on their own

Has anyone ever turned off their alarm without realizing it? I've heard of this before but it has never happened to me until this morning. I woke up and realized it was way passed the time that I should have been up. This is a very strange thing. I am wondering if it's your body's way of telling you to slow down.
As students, I feel that we work really hard at successfully completing school work. Is it really feasible to work at the same time and have some kind of social life without slowly getting fatigued to the point that you're not functioning anymore?
How are we supposed to go about doing this? It's unfair that student loans do not take into account the amount of hours we have to work to make up for the shortfall in funds they "award" us.
So, my question is.... how do you not turn off your alarm in the morning without realizing it?