If you cannot afford to pay student loans, there are reasonable options available to you. Understand this, however - one of those options is NOT to just stop paying and go into "default". If you simply stop paying your student loans, your credit will be damaged, you will be slammed with collection fees that will significantly increase the amount you owe, and the loan holder may decide to become aggressive in its collection attempts - including (but not limited to) seizing a portion of your regular paychecks. It will take your credit history a LONG time to recover from this type of damage, and you will surely regret that decision for many years to come - especially if you try to buy a house or a car, and maybe even if you try to apply for a good job.
Here's what you can do:
You may be able to POSTPONE payments by requesting a deferment. A deferment is granted by your lender when you are able to provide evidence of certain circumstances that impact your ability to pay. Common situations that generally result in a deferment are a return to school, an economic hardship and/or a period of unemployment, so long as you can document that you are actively seeking a new job. Depending on the nature of the loan and the agreement you signed, you may be granted a postponement of both interest and principal, meaning that interest will not continue to accrue during the period of deferment. More likely, you'll be granted a postponement of your monthly payments, but interest will continue to accrue. (your balance will go up as the unpaid interest accumulates)
Generally, lenders look far more positively on the deferment requests of borrowers who are not currently in default - you should be making your payments on time. Sometimes, however, a lender will permit retroactive deferment, meaning that they'll excuse a month or two of unpaid back payments.
This is very important - a deferment is NEVER given to you automatically - YOU MUST REQUEST IT FROM THE LENDER. You'll need to ask the lender (or look around their website) for the necessary application forms. These forms will identify what types of supporting documentation you may need to include with your request. Make sure that you fill out the forms completely, and include all requested documents. You're asking the lender for a favor, so be sure that you're going to show how earnest and appreciative you will be by following their policies to the letter.
If you are not able to qualify for a deferment, another possibility is a forbearance. A forbearance is simply an agreement from the lender to allow you to stop making your monthly payments for a certain period of time. Interest always accrues during a forbearance, which is why this route is less attractive than most deferment agreements. If your loan is a federal loan, there are certain classifications of "excuses" that may result in the granting of a period of forbearance - ill health, personal problems that were not foreseeable, and maybe most applicable to you, a monthly payment obligation that exceeds 20% of your monthly income.
Again, your lender must AGREE to a forbearance, you can not simply decide to grant yourself one, because of your personal circumstances. Contact the lender, explain the situation, and ask them how to go about applying for a forberance. There will probably be forms and documentation, just like with a deferment request. The lender will review your documents and make a determination whether or not to grant your request.
Can you discharge your loan in bankruptcy? Yes, but only under EXTREMELY restricted circumstances. In order to protect the perfectly legitimate expectations of the lender that the money that you have borrowed WILL be paid back, the courts are VERY VERY VERY reluctant to grant borrowers a release from their obligations. You must be able to meet a very rigorous standard that demonstrates that repaying your loan will be a SEVERE HARDSHIP. I'm confident that you feel this way already, but meeting the bankruptcy court's definition of "Severe Hardship" is extremely difficult. The court will review your income and expenses, your payment history, your employment history, look at the likelihood that your difficulties will continue well off into the future, etc. Many people have tried to get out of student loan debt in bankruptcy court, few have succeeded.
Finally, you may be permitted to cancel your student loan, but unfortunately, you probably won't care for the requirements. Student loans can be cancelled upon the death of the borrower, or the permanent incapacitation, and sometimes for a temporary FULL disability that is expected to last for more than a certain period of time.
Please, please contact your lender. Always keep in mind, no matter what the debt (well, okay, maybe not if your debt is to a bookie), that the lender would ultimately prefer to be repaid, even if it takes a lot longer than they had originally anticipated. Most lenders will shake you down a bit to make sure that you're being candid with them, but inevitably, they'll work with you to arrange for a longer repayment plan, once you've demonstrated that your financial predicament is legitimate.
A lot of what I've covered is discussed in more detail within the excellent article that I've linked below. Good luck to you - I hope this helped.