Nice WO there!
I know about that momentary lapse in concentration--IMO, it happens as the muscles suck up all the available oxygen to cope with the stress the exercise is placing on them. Not enough is getting up to the brain, so there's a momentary fogginess. Know what I mean?
You stop, breathe deeply, or put your head down between your knees, and it usually clears up.
BSSes are so hard--for me, so are walking lunges. Burn, burn!! :p