It’s all in your head.   You’ve heard it before.  From your teachers, parents and friends.  About topics from sickness to stress.  Well, the same is true of exercise.  It’s all in your head.  Your performance, that is.  You can see it in your work.  If your head is in the game, you will perform better.  If it isn’t, then you won’t.  No exceptions.  Now, what does that mean, is the question.  It means stress is mediated.  I’d say stress free, but stress is not only inevitable, but good (believe it or not).  But it can be moderated and kept under control.  It means that you are eating well and sleeping well.  If you can manage that, then your workouts and performance will be stellar.  You’ll be stronger, faster and thinner than you’ve ever been.  If you cannot manage the mentals, then you’re in trouble.  You’ll gain weight, lose strength and be generally miserable to be around.  You have to be able to wrap your head around your head.  Do it and you’ll be great.  Good luck and go get ’em.