When I had my final interview with my stake president so that I could send in my mission papers (my application to serve as a full-time missionary for the Church of Jesus Christ of Latter-day Saints), I was given two points of counsel from my Stake President.
For the first point of counsel, my stake president told me a story from long ago when he served as a missionary for the Church in Brazil. He once had a missionary companion who, in his fervor to serve the Lord, decided that he could get so much more done if he just cut back his amount of sleep. So that is what he did. At first he just started getting up earlier. This was great, and he did get so much more done with his extra time. So he set his alarm even earlier, with the same results. Then he decided that if he was getting so much more done be merely getting up a few hours earlier than usual, what if he didn’t sleep at all?
When asked how he planned to survive with no sleep, this companion replied that his faith would sustain him. (Faith, when used properly, can do many mighty things, but it was never meant to sustain foolishness.) This missionary managed to make it almost four days on his no sleep regiment before the inevitable happened. His body crashed. He became very sick, and thus useless to the work for more than two weeks.
At this point in his story, my stake president told me that the rules given in the missionary handbook (for rules and conduct) were given for a reason, including when we are to go to sleep and when we are to arise. By disregarding these rules, this missionary may have appeared to be more effective in the short run, but in the long run, he was much more of a liability.
My stake president then counseled me that no matter how hard I would be tempted to bend this rule, of all the rules, and get up early, that I must not. If I wanted to have the Holy Ghost to guide me, I needed to take care of my body, for the spirit and body are inseparably connected. If I abused my body, I would dull my senses to the Spirit and my ability to follow His promptings.
I must say that my stake president was right. I never forgot his counsel, but at one point in my mission, I did disregard it. I allowed one companion to convince me that waking up thirty minutes earlier than the missionary handbook advised was a good idea because doing so would allow us one hour to work out instead of the thirty minutes normally given. Wanting to be in better physical shape, I agreed.
Almost immediately I regretted this choice. I repented of my folly and shared the counsel I had been given with my companion. Not once, since that day, was I ever tempted to break (or even bend) that rule or any of the other rules again. And I am most thankful for having made and stood by that decision.