Failure of one often leads to distrust of all. This is the terrible responsibility of friendship. We have more than the happiness of our friend in our power; we have his faith. Most men who are cynical about women are so because of the inconstancy of one.

Most sneers at friendship are, to begin with at least, the expression of individual pain, because the person has known the shock of the lifted heel. Distrust works havoc on the character, for it ends in unbelief of goodness itself. And distrust always meets with its own likeness and is paid back in its own coin. Suspicion breeds suspicion, and the conduct of life on such principles becomes a tug-of-war.

The Art of Being a Good Friend
Hugh Black