Andrei Tarkovsky said this quote

What moved me was the theme of the harmony which is born only of sacrifice, the twofold experience of love. It's not a question of mutual love: what nobody seems to understand is that love can only be one-sided, that no other love exists, that in any other form it is not love. If it involves less than total giving, it is not love. It is impotent; for the moment, it is nothing.