I agree that love is a behaviour. But it is also a feeling. There is a heartbreaking sketch in a film called "Paris je t'aime", which is a series of short and unrelated stories.
In one there is a married man who is having an affair with some young bimbo. He is planning to leave his wife, but then she tells him that she has incurable cancer. He decides to leave his hussy, and take care of his wife, pretending to love her until she dies, so that he isn't causing her pain at the end of her life. There is a lovely line in it, which says (and I'm summarising) "he did everything he could for her - he pretended to be in love, and so, eventually became a man in love again".
When his wife dies he is left genuinely heartbroken.
Anyway, what I'm trying to say with that depressing story, is that it is possible to simply pretend to be in love. Jesus, there are enough threads on this board of women who have husbands that they genuinely believed loved them, but it turned out they've been having affairs, or shagging whores, or all sorts. That isn't love.
In my view, true love is where you can't imagine doing anything to cause pain to your partner. Because seeing them in pain would be unbearably painful for you as well. And more than that, doing something which you know would hurt them - even if they might never find out - fills you with shame and sadness.
And for that feeling to be reciprocated and not taken advantage of.
I see people have been making book recommendations - the one book that sort of encapsulated my idea of love was "The Time Traveller's Wife". The relationship between the two main characters isn't perfect - they struggle at times - but their love is absolute. I would strongly recommend it.