If your mind is strong it can carry your weak body through the gates of hell and back. If your body is strong your weak mind will never let it reach its potential. A strong mind and body is the stuff of legends. Train hard, but reflect back on it and work on the weaknesses.
When it is time to perform it is too late for shoulda, woulda, coulda. You will not rise to the occasion you will default to your level of training. I once read this somewhere and I dont know the source "In combat one man is much the same as another, he who is best is he who is trained in the severest of schools." The severest of schools are always more mental than physical. To summarize: train the brain to fight and win, train the body to keep up. Yet another simple truth from survivology101.