I confess to not having read the whole thread, but I still might, so for now, I'm just going to answer the question: What does Se mean to you?
To me Se is being here now.
As a child I rode horses bareback and Se, I think, was moving with the horse, feeling his body shift beneath me and instinctively knowing which way to lean or hold my body. It was climbing a tree and feeling the bark in my hands and moving naturally from branch to branch or up the trunk, digging my bare toes into the rough maple bark and then sitting on the limbs, eyes closed, feeling the wind, hearing the birds, breathing the smell of the woods or simply declaring to my brothers, "I'm up here. Your turn now!"
When I was a teen I used to go to dances. I won a contest once. I won it because when the music played, I was one with it. I had no lessons. I simply merged with the beat and moved in ways that came naturally. I have always had the ability to totally get lost in a moment, but never to the point that I didn't think about the consequences of my actions, if that makes sense. I have always been a risk taker, but all of my risks were always "calculated."
Martial Arts is much the same. It's being in the moment, perceiving the most subtle shift in your opponent's movement or eyes or breathing and adjusting before they make their move. It's going by your gut but never loosing your mind.
In art it's being aware of the colors and shapes and shadows; it's curving the lines without thinking or making the shadows without really having to think about it. It's the ability to create what you see in the instant you see it whether you see it in the world around you or just in your memory.
As a writer, it's being so at one with your surroundings that you can remember every detail in a room, every smell, every sound or the way the smoke hangs in the air.
I have an incredible memory for sensory details, for the clothes people wear, the way their faces look, the houses they live in, the color of the sky.
It's using a tool, like a chain saw or a knife or a hammer or a steel whip and not separating myself from the tool but having the tool become an extension of myself, like a limb.