The platinum rule: do unto others as they would like to be treated. And, yes, that is (within limits, for we don't want to give the alcoholic more alcohol) the essence of religion.

I don't know Tolstoy but we are only responsible for loving others; if they don't return it that determines their outcome, not ours. Love is the opposite of selfishness so to require something in return is not love at all but some kind of manipulative transaction. That doesn't mean it doesn't emotionally hurt when someone treats you cruelly.

And 'Nature Boy' by Nat King Cole is a great, great song. It's amazing when a song can embody wisdom. My favorite is Louis Armstrong's "What a Wonderful World" with his spoken word intro:

"Seems to me, it aint the world that's so bad but what we're doin' to it. And all I'm saying is, see, what a wonderful world it would be if only we'd give it a chance. Love baby, love. That's the secret, yeah. If lots more of us loved each other, we'd solve lots more problems. And then this world would be a gasser."