Basically, this was from applying the Anaconda Choke. I did it the way I have always done it, got a few taps from it and as how it was shown on the internet and as How I have seen it done by others. However this time something went wrong. Okay, I am 130 pds and he was about 170-180 pds. I was sprawled on top of him and he was in a kneeling-sprawled position under me. I had my hands/arms snaked in right, my right arm circling his neack and right arm/shoulder, with my right hand on my left bicep and my left arm flexed. So now I was then trying to turn myself anti-clockwise, the proper technique for the anaconda, and he was resisting. This me trying to turn and he trying not to turn lasted about 5secs. My head was on the side/edge on his body. You can call it the corner of his back and side. Basically too both of our upper body was quite near the floor too. Then All of a sudden, he tried to flip himself over. What resulted was my own pent up force of turning anti-clockwise drove my own head to the ground, coupled with his body crashing into my head too. I briefly blacked out from it. I could not concentrate on much things after that for the rest of the day. I felt slightly dizzy with a little of headache too. However, now it is the second day and Most that remains is a slight dazedness. I do not think I will do that technique anymore. I am wondering whether you have techniques toi refine it.