A sane man, therefore, is always fearful of falling from his position. This is a regulative principle. One should not fall from his exalted position. The highest goal of life can be achieved as long as one's body is stout and strong. We should therefore live in such a way that we keep ourselves always healthy and strong in mind and intelligence so that we can distinguish the goal of life from a life full of problems. A thoughtful man must act in this way, learning to distinguish right from wrong, and thus attain the goal of life.
From Srila Prabhupada's purport to SB 7.6.5