Love

Love is guidance towards character. That is to say, to love someone is to desire to guide him towards good character.

This is why you can't love God.

This is why you can be lonely despite appearances and despite many seeming friends.

In order to love a man it is necessary to know who he is. A man who is not understood by any of his acquaintances is unloved. This is how a man whose acquaintances are all myopic, narcissistic, mentally ill, or similarly vicious, can be unloved despite appearances.

UPDATE: Caveats that go without saying: 1. If you're paid to mentor a person toward good character that's not love. The desire I'm referring to in the definition is an ultimate, non-instrumental desire. 2. You can, of course, be deeply grateful to God and devoted to virtue in light of that gratitude.