As Aquinas has pointed out, talking of God usually tells us more about us than about God. Yet as described, the whole God thing sounds rather appealing, especially that last part about being in love and divinely happy.
The question is, how do we get to be like that? The answer to this question goes right to the heart of Aquinas and is what he spends the Second and Third parts of the Summa Theologica explaining.
And guess what, it really is about being happy. That loving relationship between God's self-awareness and God that we call the Trinity is what we are supposed to model, by seeing, understanding and loving the known world and through it, God. This ongoing act of mind and heart gets us as close as we can to being one with the mystery of life. The wonder and delight we then experience helps break the hold of ego on our perception and opens us to bliss, the human version of divine happiness.
The whole purpose of Christ, the Incarnation, Church, Eucharist, and all the rest is simply to get us into this graced state, and how this all works is what Aquinas labors to explain in the rest of the Summa Theologica. So buckle up; we're about to plow through it, starting with a further discussion of the whole concept of happiness.
"To know something with the mind is to understand what
it is; so the mind is fulfilled to the degree to which it knows
what things are. ... We call it wonder and it drives us to investigate
until we are satisfied with our understanding of what that cause
is. For complete happiness then the mind wants to know the nature
of the first cause of everything."