Love is the movement toward union with the beloved, and delight in the beloved so united.
If I love ice cream, love is my steps toward the store to buy it, laying out 5 dollars, and walking home with it. Delight is then the operation of satisfied love (union with the beloved) where I engage in consuming the beloved.
Emotions are movements of the lower appetite (not the will), and in the emotions, the proper term for what most would term “love” is actually “desire”.
To love God with my whole soul, whole heart (or will), whole mind (or intellect), etc., it is first necessary to have an understanding of what union with God “would be like” (just as I have an image in my imagination of what it would be like to be tasting ice cream).
And that image or understanding of what union with God would be like, must be understood as “very good”, ultimately good (or, “very desirable”, “ultimately desirable”).
Then it is necessary to understand or to know that union is a real possibility. This is made possible by “grace”; first in that our initial union with God happens in material reality - we meet Jesus (in person / in his Church), and find union materially with Him there (we ask to be joined to his Kingdom, and we are baptized). With this baptism we are given the Holy Spirit, infused with divine Virtue, and taught what we can now do with those virtues of Faith, Hope, and Love. Now we have the understanding of the desirability of union with God, and we actually have the union - the Holy Spirit with us, and we have the new nature of virtue, where we are able to delight in the union; we are able to do the things we do virtuously, rather than moving wherever appetite might move us at any given moment (they move us toward union with wealth, pleasure, honor, power). Whereas with single hearted love of God, you use the Virtues you have as you do things in the world, you do all your doings virtuously, and “in delight” because you are one with your beloved, you are united right now.