I have had the following experience on the cushion perhaps a dozen time in the past couple of months...

I'm following my breath, essentially in a concentration practice approach. The experience gets very powerful and consuming, and then Somewhere around 15 minutes in, pop! It's gone. I am exquisitley alert, but not connected to anything. From that point on, I find the effort to follow my breath, or to meditate at all, moderately annoying. Things feel two dimensional. The closest analogs to this feeling in my life are the starker realities one sometimes encounters after orgasm or, farther back in my past, after 'peaking' on certain narcotics. Recently, the moment before the bubble bursts has beem accompanied by a very strong visual--a mountain range, somebody's back yard seen through a screen door, my hands covered in blood (my own I think, and not disturbing), an empty city block.

What is this experience? Given how difficult I have found returning to concentration from here, what do i do next? Do i work to avoid it? Do I sit with the annoyance? I have tried. It hasn't produced much. Or, as I have recently wondered but am yet to implement, is this moment an opportune time to transition to wisdom practice?