Unfortunately, we are attempting to understand something that is beyond the capacity of the levels of human that we are most aware of and use to understand the world around us.
Consider that our brains are subdivided into various parts and structures and that each gives humans capabilities that animals whose brains do not have these parts naturally do not have.
It is possible that the human brain doesn't contain the part(s) that would give us the capability and capacity to understand the Holy Trinity.
Otoh, it is also possible that we humans have all the parts we need to understand the All, everything except for the 'juice' to power it up, that is.
Or, it's also possible that the parts are all there and it's got power, but we humans haven't figured out how to turn it on.
Or, it is also likely that we have all we need and it's all powered up all the time, just waiting to be used.
Because, it's very possible, in a Proverbs 11:14 kinda way, that we are clueless, and so distracted and upset with things while looking left and right, that our inner interference is so bad that we think those parts are broken or simply not there.
As such, for many God exists, but isn't "there" for them personally,
And for many others, the Holy Trinity just simply doesn't exist at all, other than maybe as fantasy fiction.
I believe the last possibility, the clueless, distracted and upset possibility, is the truth of our "truth".
None the less, we often say of our human selves that we are "body, mind and spirit", and this seems a good human translation of our being created in Their Image.
Here is were I had to look elsewhere for some additional info to interlace the pieces I've found into a complete (for me, anyway) picture.
It's hard to put into words or to find a good metaphor or analogy to picture it with.
In a way, the human being that God created in Their Image is kinda like a seven section, two-way "rain chain" that is connected to earth on one end and Heaven on the other.
Rain flows top down with a rain chain, so the analogy isn't perfect, as communication flows up, down and in between Heaven and the levels of the human hiearchy.
For most of us, and certainly this is true for me, our consciousness and awareness for the most part exist in the lower 3 levels: the physical level, the emotional level and the mental level, from lowest to highest, with the physical level, the existing at the lowest frequency, connected to the physical plane of our existence.
To illustrate this multi-leveled concept, we say it's "my body" or "my emotions" or "my mind" indicating that some part of our being recognizes and understands that there are separate parts and each is distinguishable from the others.
Moreover, we realize through experience that each of these levels influences the others, but that they each have their functions and their level/place within the hierarchy.
However, there are four additional levels of the human hierarchy that many, or even most of us, are not aware of in our day to day consciousness.
The next highest level above the mental level, the 4th level of the human hierarchy, is the intuition.
The level of intuition is also called the "intuitive bridge", as it is situated between the lowest three levels and the highest three levels of the human hierarchy where it functions as the bridge between the upper three levels and the lower three levels of our being.
Conceptually, I like to think of the intuition as being like the area between/connecting air and water. The intuitive level is the space between that connects two different states of our being.
The upper three levels of the human hierarchy, the spiritual levels, are of a much higher frequency of being than that of our lower three, and naturally they are completely different aspects our being.
"God is Love."
Our upper inner three levels are levels of "Love" connecting us to Heaven, and like with the physical, emotional and mental levels, each are separate and distinct parts of our being.
One level is "Agape", but I don't remember the names for the other two levels or where each of the three are in the human hierarchy.
The intuitive level between the upper and the lower, the "intuitive bridge", allows the conversation between the two different states of our being the upper level and the lower.
Many have a well-developed intuition. Others deny the intuition even exists. I believe it is by the "intuitive bridge" that we are aware of the "still, small voice" coming down to us in the physical plane from Heaven above.
Unfortunately, this area is where the undisciplined ego likes to hang out. If the ego is unhealthy, and has taken over instead of being a servant doing its job, it becomes like a bridge troll, turning the intuitive bridge into it's very own troll bridge, and claiming, influencing or denying all traffic that normally passes over the bridge between the upper and lower.
Naturally, for this reason, the ego is the FAVORITE target of Satan and turning the ego into a troll is likely his favorite pastime.
Convince the ego to cut off communications to/from up above and the human will eventually die of starvation or commit some form of suicide in the valley of death.
This is my attempt to understand things so far and is a work in progress.
You might think all of the above is something heretic, and for many people it might be, I really don't know.
Actually, IIRC, the above 7 level description/understanding is Hermetic, not heretic, but whatever.
Whatever one calls it, for me, it is descriptive, and thus helpful for my understanding both the Trinity and we, the created in Their Image, human beings.
The mental level is higher in the hierarchy than the physical and the emotional levels and it is designed and placed to rule over them.
If one is disciplined, the mental level can and will do what it's told, and then it and the emotional and physical levels will all go where the mental is focused.
If one sets one's mind on the higher things of Heaven, the "God is LOVE" stuff of our higher three inner levels, then the lower three levels will become quiet and all will align and harmonize with the higher thoughts.
We are then living "in the zone" and the result is like the beautiful music of well-harmonized chord, with all notes in tune and played in harmony.
For this reason, we practice, practice, practice the notes and patterns of His Teachings and the music of His Way, so that the intuitive bridge becomes like a two-way mirror where we no longer see our own image, but instead we "see" Him and He sees His Own Image in us reflected back.
If not, then the notes and chords played are out of tune and discordant, and generally destructive to the patterns and music of that person's life and purpose.
In those situations, the intuitive bridge is probably functioning instead as the ego's mirror and that's why we seem so full of ourselves in those times.
No surprise that the ego wants to like it that way, but that's not what it's designed for and it can't be satisfied by being in charge.
Satan keeps that part a secret, but it's not like the ego would believe it anyway.