Boot Camp is all about surviving the mind games, the physical stuff is not nearly that bad, though it has gotten tougher over the last few years. Remember now adays pull ups are dead hang all the way up and all the way down and sit ups you can not raise your ass off the ground.
Never quit, no matter what happens no matter what is said or done, keep on trying. They will test you and will try and break you, just never give up. And learn the history before you go, it helps a hell of a lot and I am not happy it is not as well taught now a days as it used to be. History and belonging and knowing went went before all help make a Marine what they are.
Knowing if you fail you fail all those before you and not just yourself is a BIG motivator. And I do not mean in Boot Camp. Be ready to play politics if you get promoted. I suspect even with the war on the petty little political games still go on.
Never understood the concept of " How you look" being more important then " what you can do" but you will get officers and SNCO's that think that way. And running is a biggy, I was never very fast, was lucky to do an 8 minute mile and usually was slower than that. There will be Officers that think if you can not run REAL fast your failing somehow. They will do crap like formation runs where they expect everyone to run about 7 minute or faster miles and then get pissed when half the formation slows down on them. Just live with it if your not one of the fast ones.
What till you get a moronic SgtMaj that takes a Battalion on a run at a 6 minute clip through paths so narrow only one person can run there and then gets upset he strung the battalion out for a mile. The farther back your company is the faster you have to go to catch up on shit like that and at those speeds, YOU can not catch up.