You don't have to be hypostatically united to the Godhead, but it helps
In Book XIV, Chapter 8 of his De Trinitate, St. Augustine writes that the human mind is God's image
in this very point, that it is capable of Him, and can be partaker of Him; which so great good is only made possible by its being His image.
This is, as far as I can tell, the source of the term "capax Dei," which refers to the doctrine -- or maybe it's just an observation -- that, through his reason, man is able to know and love God.
Also, [God] does not have only care for man, but He has a familiarity with him; and this why [the psalmist] says, "That thou art mindful of him." [v.5] Only the rational nature is capable of God [Sola natura rationalis est capax Dei], to know Him, and to love Him. Inasmuch therefore as God makes Himself present to us, by love or cognition, He cares for us: Job 10[:12b]: "And thy visitation hath preserved my spirit."
Man's capacity for God is, of course, most perfectly demonstrated by the man Jesus. There's a lot of theological speculation about Jesus' human knowledge of God, but we shouldn't neglect His human love of God. Moreover, devotion to the Sacred Heart of Jesus shouldn't neglect the fact that, with the same human heart with which He loves us, He loves the Father (and Himself, and the Holy Spirit).
Knowing that we are capable of God, and having Jesus as our example of that capability, what sort of false self-love must we have if we settle for less than God?