You'd probably die a hero's death and I guess some folk would prefer that over dying all alone in bed.
(Old soldier mode) - There's nothing heroic about dying and it's always something you do alone - (Old soldier mode)
But I was of the same mind before I joined, there is a certain romance about war. It doesn't survive your first battle, but I suppose that's part of why so many people join. There's a certain expectation that it (death or being maimed) wont happen to you, but that's just part of being young. It doesn't have to be war, it could just be a person smoking, or doing stupid stunts. That's the whole point about being young isn't it? You get to live without fear because you are invincible!
Sigh, it's a long time since I had that feeling...
You soon get used to the lack of sleep and you'll notice a big change once you are out of training. Sleep, or lack of it isn't the worst thing. It's the repetition. Painting grass green because a VIP is visiting, or doing endless drill because you've been dikeed to do yet another parade, now these are the things you'll learn to hate. Top tip? Join a sporting activity that you are good at (I picked mountain climbing), you'll find yourself on expeditions or sporting tours more than you'll find yourself being a soldier. While your lazy buddies are painting grass, you'll be on a six month expedition in Nepal or teaching some kids how to play basketball in Peru. If you embrace your service, it will embrace you.
And pick yourself a trade that will have a use on the outside. Loading missiles onto aircraft isn't a very useful skill to have in civvy street.