There are a lot of good reasons for getting into an MFA -- a Master of Fine Arts -- program. It really can help your writing. There's no guarantee that it will, but you'll be working with people who have had a lot of experience in bringing out the best in young writers, and if you click with the right person or people, you may find yourself saying at the end of the year, "she/he brought things out of me that I didn't know were there."
In an MFA program, you'll have the stimulation of being around other people who care about writing. A lot. And -- no guarantees -- but meeting and hanging out with people who care as much about it as you do can make you care even more, write even more, challenge yourself even more.
You can learn -- no guarantees, but if you take the program seriously, there's a very good chance that you can learn to edit yourself, to criticize yourself, to hone that super-important tool that my great teacher, Donald Finkel, called a "bull---- detector."
Maybe you'll get a job out of it. No guarantees.
And on the negative side? People say that all writers who go through an MFA program come out as if through a cookie cutter, but this simply isn't so. If your individuality matters to you, you're not going to lose it.
If you spent those three years panning for gold in Alaska, driving a 18-wheeler, or fighting mercenaries in a third world country, you'd have more to write about. This may be true. MFA programs don't necessarily turn out cookie cutter writers, but they do turn out writers who've had more or less the same experiences over a three year period. On the other hand, if you're driving an 18-wheeler back and forth across country, you might never have time to write, and if you're fighting mercenaries, you might be dead.
And the main negative? There are no guarantees.