The same Supreme Self has become all the souls. When thus there is a multiplicity of lives, the mAyic drama of mutual distinctions takes place.
And at the same time, in the opposite direction, there is a welcome supreme force dispensed by the Grace of the Almighty, that helps to unify all the distinct elements; this is what is called Love.
Usually human tendency is to gain something from the other person. The opposite cure for this is Love, that produces a sense of fulfilment by giving oneself to others. This is the difference between Desire and Love.
When we like something it means that we obtain a satisfaction/happiness for ourselves from it. But when we love something or some one it means we give satisfaction/happiness to that something or some one.
Desire implies receiving; Love indicates giving.
Our happiness happens only when the other being has some treasure of either form (rUpa) or of quality (guNa), or, even, of money; only when the other being has one of these or something similar that we may acquire, we get the happiness that we expect.