DO NOT do what I did!
Do NOT cut yourself off from your friends and family no matter what you do. You will need them more than anything when you get home. Sure, when i was over there
(4 years in Iraq, first deployed in 2002), I got stronger, I got harder, I got meaner. Things didn't bother me. When I took a shot, when I helped a casualty.. When the going got tough I got tougher... But I regret it more than anything now. After years of silence I am now so disconnected from family and friends that I do not believe those relationships can be repaired.
Talk to them as much as possible, every opportunity you get, but be sure to leave them back home whenever you leave that gate if you want to make it back home in one piece. Get a laptop, a webcam. For the physical stuff, You're going to want to run a lot, push ups, sit ups, pull ups, anything for endurance. Lots of cardio. Eat right, when you get over there don't pig out on short order. Get some real food in you, It'll keep you alert when you're out on patrol.