Pythagoras asks that we not let a friend go lightly, for whatever reason. Instead, we should stay with a friend as long as we can, until we're compelled to abandon him completely against our will. It's a serious thing to toss away money, but to cast aside a person is even more serious. Nothing in human life is more rarely found, nothing more dearly possessed. No loss is more chilling or more dangerous than that of a friend.
Thomas MooreWith what a deep devotedness of woe I wept thy absence - o'er and o'er again Thinking of thee, still thee, till thought grew pain, And memory, like a drop that, night and day, Falls cold and ceaseless, wore my heart away!
Thomas Moore