1. My strength is not your weakness. My weakness is not your strength. A strength that finds itself only by taking advantage of my weakness is no real strength. A grown man does not prove himself by boxing with an infant.
2. Strength is a relative, and not an absolute, term. It is always strength to do such-and-such, or strength in relation to such and such. My arm is strong compared to an infant's but weak compared to a steam-hammer. To say so is to make more than a literalist or merely descriptive statement; because understanding that there is no such quantity as a reified 'perfect strength' (any more than there exists 'perfect goodness', 'perfect love', or 'ultimate evil' -- all of these being relative terms) frees one from the tyranny of hating one's own weakness. One's weakness is a necessary part of one's strength, and vice versa.