Ralph Waldo Emerson said this quote

The purpose of life seems to be to acquaint a man with himself and whatever science or art or course of action he engages in reacts upon and illuminates the recesses of his own mind. Thus friends seem to be only mirrors to draw out and explain to us ourselves; and that which draws us nearer our fellow man, is, that the deep Heart in one, answers the deep Heart in another, -- that we find we have (a common Nature) -- one life which runs through all individuals, and which is indeed Divine.