Love is by definition "to will the good of the other", and action follows if capacity exists. It does indeed involve attitude, but an attitude that does not result in according action if the capacity exists is proven disingenuous. Likewise, reciprocity is proven disingenuous if the reciprocator develops resentment.

The commandment goes above the natural law of reciprocity and perfects it.

I don't mean to imply, although I may have done so accidentally, that Christianity invented reciprocity. I do, however, claim that reciprocity isn't completely universal. Cultures in decline begin to reject it along with other elements of natural law, and so accelerate their demise.