My former male self always found the dissociation periods to be rather enjoyable...at least he wasn't in pain. It took me a few months learn how to come back when requested. Now it's just a chronic low-intensity derealization...because my body is at last mine.
I was taught to focus on something nearby, like a desk or a chair...something I could touch, feel, sense...and starting with that touch, tell myself/selves that "we are here, we are real, this is 2014...", and anything else that I/we felt was necessary to accomplish the goal of "being" back in the the*apist's office. I had to remind myselves that he (the the*apist) meant no harm, he wasn't going to touch us, we are safe here...and most of the time that reassurance allowed the defense of dissociation to minimize.
That is fundamentally what dissociation is...a defense against overwhelming sensory or emotional input.
Hope this helps...*hugs* if safe.