Every day and every hour, every minute, walk round yourself and watch yourself, and see that your image is a seemly one. You pass by a little child, you pass by with ugly and spiteful words, with wrathful heart; you may not have noticed the child, but he has seen you, and your image, revolting and godless, may remain in his defenseless heart. You don’t know it, but you may have sown an evil seed in him and it may grow, all because you were not careful before the child, because you did not foster in yourself a careful, actively benevolent love. Love is a teacher; but one must know how to acquire it, for it is hard to acquire, it is dearly bought, it is won slowly by long labor. For we must love not only occasionally, for a moment, but forever.
Source: The Brothers Karamazov, as quoted in The Gospel in Dostoyevsky