Knowledge is the treasure of the mind, but discretion is the key to it, without which it is useless. The practical part of wisdom is the best.
Owen FelthamNo man can expect to find a friend without faults; nor can he propose himself to be so to another. Without reciprocal mildness and temperance there can be no continuance of friendship. Every man will have something to do for his friend, and something to bear with in him. The sober man only can do the first; and for the latter, patience is requisite. It is better for a man to depend on himself, than to be annoyed with either a madman or a fool.
Owen Feltham