Three levels of love of God
St. Thomas Aquinas, in his work On the Perfection of the Spiritual Life distinguishes three essential levels of love of God: (1) God's love for himself; (2) The love of the blessed saints and angels for God; (3) The love of those in grace and charity on earth.
(1) God is infinitely good and infinitely lovable, but no creature can love infinitely, and therefore only God himself can love himself as he deserves: the Father's infinite love, which he shows to and bestows upon the Son and Spirit, is supreme love.
(2) Creatures love God perfectly in heaven, inasmuch as all of their power and activity is turned to God: their attention is upon him, they see him as he is, their hearts embrace him, and they do all things for his sake.
(3) We here on earth can love God perfectly in the sense that we give ourselves to God, and thereby, since all our actions belong to us, we implicitly give all of them to God and do them for him, even if we don't and can't think of God at every single moment. Again, we love God perfectly inasmuch as we submit our minds entirely to him, believing his Word which he speaks to us, and give our hearts to him, loving things for the sake of God, and acting out of that love.
A basic form of this third level of love is required of all of us; it is wrong to disbelieve even a single word of God, to refuse to follow even a single one of God's precepts, to love anything other than God as though it were our ultimate happiness.
Yet within this third level there are various degrees. We may approach more or less closely to the second level of love, inasmuch as we strive to have our hearts and minds always turned actually towards God. St. Thomas explains that this is the purpose of the evangelical counsels: to take away everything that could distract us from giving this actual attention to God.
The more man's affection is withdrawn from temporal things, the more perfection will his mind be drawn towards the love of God. Therefore all the counsels, by which we are invited to perfection, aim at turning away man's affection from temporal things, so that his mind might more freely tend towards God, contemplating him, loving him, and fulfilling his will.
1. God's love for himself is absolutely perfect and infinite.
2. The most perfect love possible to creatures is the love of created persons for God in heaven; the whole strength of their nature is directed towards God.
3a. Perfect love possible on earth (generically): we refer everything to God, but not necessarily consciously at every moment.
3b. Most perfect love possible on earth: to strive to imitate the perfection of love in heaven; to seek to act at every moment out of love.