well, i don't want to conflate love and passion here. but i do understand the idea of obligation being a kind of stable foundation for love—is this what you mean?
i don't disagree with what you're expressing here. there is a sense of obligation in love, it just shouldn't be the motivating force.
for example, i feel obligated to get my Wife an anniversary gift. the gift will differ depending on whether i'm only doing it because i feel obligated to get Her something or whether i want to genuinely express how grateful i am for Her.
that motivation—that intention is going to be felt in what i choose, how i give it, and how She receives it.
your responses are very appreciated, btw. ^^