If I really can't make my payments, is there anything I can do?
Fortunately, yes. Your options range from having your loan canceled, which means you will never have to pay it back (be warned: very hard to do!), to getting either a deferment or a forbearance. What you can or can't do depends on what kind of loan you have and the reason you cannot pay.
Under what circumstance can a student loan be canceled?
A student loan can be canceled if you are permanently disabled or die, or under certain other circumstances that also apply to deferment.