Don't join, especially not as a grunt. Go to college, get a masters degree, and after that... if you still want to join, you'll enter as an officer (captain+).
As a grunt, you make no difference. You're a pawn in someone else's war and you will most likely come out in a bodybag, physically disabled, or suffering from ptsd for the next 10+ years.
War is not an adventure, it is an experience in total, [crap]-in-your-pants, horror. You watch your friends die from gut wounds that make you think of your mother's spagetti, you carry with you the questioning eyes of the kid you shot, his lips forever voicing some words foriegn, haunting you for decades after, "what did he say, what did he say?". You will find your weapons frequently jammed, adding to the fear of the moment when every single shot counts. And when you rise up to take a shot, if you are not shot in return, you will find no targets. Only human beings acting with the same deluded feelings of honor and purpose.
What is a truer purpose, but that of providing for your children, being there for your parents, sharing your life with the one you love? Fighting on foriegn soil does not bring purpose to your existence, it strips it raw, leaving you with a hollow core of inner turmoil. If you do battle, take lives in conflict, you will learn about yourself that which would have been better left unvisited. Like a crime of passion, a crime of lust, it will change you forever, destroying the many opportunities you presently hold in your hand. It will leave you with little more than the memory of the crimes you personally committed, of those you witnessed, and of the hardship you will have to endure for having volunteered to participate.
And if these words mean nothing to you, I'm sorry.