In order to teach me about the existence and nature of heaven and heavenly joy, the Lord has given me the opportunity to perceive the pleasures of heavenly joy frequently and for extended periods. Because I have learned these things by actually experiencing them, I possess the knowledge but cannot possibly put it into words.
To offer just an idea of it: The countless pleasures and joys there, which come together to create a single experience shared by all, carry with them a certain emotion. Within that common experience, or that common emotion, are points of harmony among a boundless number of feelings. These individual points of harmony do not come clearly but only vaguely to our awareness, because our perception is extremely generalized. Even so, I was allowed to perceive that there were countless parts, organized in a way that can never be described. Those countless parts flow from the order that exists in heaven, which determines their nature.
The smallest individual elements of an emotion are organized in such a way that they are presented and sensed only as a collective whole, according to the capacities of the person who feels the emotion. In a word, every whole has an unlimited number of parts, organized in the most perfect way; every one of the parts is alive; and every one of them affects us, all the way to our inmost recesses. For the inmost recesses are where heavenly joy comes from.
I also perceived that joy and pleasure seemed to come from my heart, gently permeating all the inmost fibers of my body and thus all the bundles of fibers. The sensation of this joy at the deepest levels made it seem as though each fiber was composed of nothing but joy and pleasure and all the perceptiveness and sensitivity that come with joy and pleasure. The fibers seemed alive with happiness.
The joy we feel in physical indulgence, compared to these joys, is like a coarse, stinging dust compared to the gentlest breath of pure air.
from Secrets of Heaven, Volume 1, Section 545