During sleep your body has time to repair the muscles that where used during the day. So if you work out getting a solid 8 hours a night is a must, or else you will feel even more fatigued and worn out the next day then you are going to anyways.
For want of a nail, the horse was not shoed.
For want of a horse, the message was not delivered.
Because the message was not delivered, the war was lost.