I used to stare at the bubbles in my bath when I was about 4 or 5, imagining that they were whole galaxies; each reflection of light stars, with their own worlds, and people, and girls sitting in a bathtub of galaxies. And how much faster their universe must be if when I pulled the plug their entire sky of stars went swirling down the drain. Millions and billions of years in the flash of a second. I'd stay in the bath long past time it was cold cold cold, just to give them more time.
Ditto would sit in class, or run alongside my friends and enemies (curious how enemies were the natural order of childhood), trying to figure out what made me me, and them them, and how we were different (or were we?). Did I end at the surface of my skin? Did they? What made us each us? Or were we? Could we change for the wanting of it? Who were we? Why? How?
Similar, swinging, legs forward and back / higher & higher, trying to catch the moment behind me or the moment ahead of me. Vexed, infuriated, that I seemed stuck in this moment in time. That no matter how fast I leapt from the seat & let go of the chains, I could never look back and catch sight of myself poised about to do what I just did. That I could watch the stars move, and the sun rise, but could never actually see the passage of time. Only the markers of movement. That when I closed my eyes, that all vanished. Today. Tomorrow. Yesterday. Nothing made them unique, and distinct. And I couldn't change my -or anyone else's- place in it. No matter how hard I tried. So I kept trying. Yet it all seemed so artificial. As if this was something someone had invented, and laid down the rules, without any thought as to the consequence of being forced to stay fixed in any moment. Unnatural. Linear. Disorderly. It simply made far more sense for time to be three dimensional. But since I couldn't see it? Couldn't grasp the edges? I was stuck. I didn't hear this quote for a long time, but it sums up my frustration; "Time is like the pages of a book for you, isn't it? All pressed up against each other, able to flip though them in any order, and at will. While I, weary traveller, must take the longer route."
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<grin> That's what your thinking reminds me of. The very serious business of the imaginings of childhood, stretching to understand the world around them. Now, I have a comorbid disorder that includes disassociation as a part of it, so I can't say for certain that disassociation isn't a piece of that. But, for me at least, it was very much the opposite of derealization; as I was trying to understand what made things real. The world wasn't real, as yet, and I was trying to make it so. Things coming into focus for the first time. Object Permanence & Abstract thinking was difficult for me. I had to be able to touch it, to see with my hands & not just my eyes, or my minds eye. If I couldn't define the edges, I needed to. Needed the words to describe it. (Part of that is I was bilingual when I was little, and knowing the right words was important, but also confusing. Things needed names to be complete. Was often accused of babbling, as I'd mix my languages up.)