You don't go into the military because you want a better job when you get out, or because you need money for college, or because you think it will help you grow up, or straighten you out, or any other outside reason. You go in because you want to serve your nation by subjecting yourself to that nation's military culture which though evil by nature is necessary for the very existence of the state.
Good soldiers know that from the get go and it makes a whole lot of it hella easier to get through. Some of what people above has said is kinda close to the truth. But in reality none of it comes close because the military is a separate culture, one that relies on itself, one that is pretty much closed to outsiders (the military sees the entire world as military or not - solider or civilian, to them its the only distinction worth noting). Military life is traditional, with roots going back to Greece and Rome. Weapons change, sort of, nations and states and empires come and go, military life really doesn't change all that much in time or space. Being a solider in the American Military is much closer to being a Russian solider, than either solider is to being a civilian, and both share a culture where that reality has always been pretty much true. They would understand the rhythm and nature of the Roman Legions more than they would that of Rome itself.
And no matter if you are a nurse, a chaplain, a med-tech, or a clerk typist, you are a solider first and foremost, everything else comes second to that. If you don't want to be a solider, and end up - as often happens to soldiers - in a war where people you don't know are trying to kill you, as you try to kill them you might want to rethink. We are waging two different wars, and neither seems to working its way to an ending any time soon. So its something to think about.
People talk a lot about the kind of mind control, and there is some retraining, but most of the the mind control is in the form of groupthink on the part of the officer corps. The guy who fixes jeeps in the motor pool doesn't have to be 'sold' on the mission or the strategy or tactics, all he has to do is fix the vehicles. But the officers have to all be on the same page. And there is - this is the culture deal working - a real stress placed on getting everyone on the same page and keeping them there.
All the military officers I knew and taught were constantly among the best and brightest students and people I've ever known. They are as a class, highly educated, extremely motivated, and personally driven people. They also share another common characteristic, they believe 100% without waiver or doubt in what they are doing.
