Your best bet is to contact the lender.
They need to know why you can't pay.
You can request a deferment or forbearance based on your situation.
If you are back at school, you can have your payments deferred until your withdrawal date.
Don't default on your loan. It's no one's business but your own but if you are delinquent, any name you listed as a "reference" on your application will get phone calls from your lender. Sometimes its not even the original lender, it maybe a secondary market that purchased your loan.
You friends/family as your references will not understand when they get the phone call and think that they will be responsible for the loan. They're not. They're basically looking for info on where to send those lovely computer generated letters looking for you.
Oh, and if that person has moved or number changed, they'll still find you. A good skip tracer now has more advantages with the use of computers. I've found people locked up in prison and had it verified so it's possible.
I have a friend whose loan payments are outrageous for her masters so she's deciding to quit teaching and going back to school.
I hope you understand the ramifications of defaulting on your loan. An additional collection fee of 25% can be added on for fees as well as the IRS having the ability to withhold any refund. The DOE (Department of Education) can sue you for defaulting on your loan.
I hope everything works out. Stay in contact with your lender and ask them your options.