Thinking about writing is simple. Picturing yourself sitting down in front of a computer screen, hovering over a blank sheet of loose leaf, pen in hand- that's the easy part. Fingers against keys and pen to paper- that's a totally different experience.
Being lost in your words is what I think being in a coma would be like. You know that life is going on around you, you are aware of whats happening but lost inside yourself. Do all writers have this out of body feeling? Upon revisiting their words, do they question where such intense imagery comes from? If those particular details grew from their own memories, dreams, where?
A piece of writing is never truly complete, years later you will want to change a comma to a period or a noun to a pro noun. The writer's journey to perfection is never finished, but upon reaching that final sentence for the first time, feeling your thoughts come full circle- a wave of adrenaline rushes against you. A feeling that can last and last, but afterward feels so distant. You're not sure how you got there, but once the hangover sets in, you feel empty, tired, released.
The rush of looking at a page that was once empty but not full is unexplainable. Ask a drug addict how to explain the euphoria of their first high, a marathon runner crossing the finish line- its all a fog until it's over.