I can’t really comment on this passage extensively, because I’m not absolutely sure I fully understand it myself:
Lovers and friends have two desires. One is to love so much that one enters the other to make a single being. The other is to love so much that with half the earthly globe between them, their union would not suffer any diminishment. Everything that we desire vainly here below is perfect and real in God. Those impossible desires are within us as a mark of our destination, and it is good for us when we don’t hope to accomplish them.
Love between God and God, which is itself God, is the link of a double virtue; this link that unites two beings to the point where they are indistinguishable and really are one soul, the link that extends itself across the distance and triumphs over an infinite separation. The unity of God where all plurality disappears, and Christ’s abandonment of belief in being found, yet without ceasing to perfectly love his Father — these are forms of divine virtue of the same love, which is God Himself.
God is so essentially love that unity, which in a sense is its actual definition, is a simple effect of love. And corresponding to the infinite virtue of unification of this love is the infinite separation over which it triumphs, which is all of creation, spread through the totality of space and time, made of brutally mechanical matter, interposed between Christ and his Father.
— Simone Weil, “The Love of God and Affliction” Awaiting God (pp. 37-38). Fresh Wind Press. Kindle Edition.
The oneness we desire in love is something we never fully experience in this life. But, it is a pointer. It points us to who we really are as beings created in the image of God. It points us to God — in whom alone are we will find the fulfillment of our deepest longings and desires. Thus, having unfulfilled desires is a good thing — and important aspect of being human.