Easier trick: when you feel you're about to reach the point of no return, touch the tip of your tongue to the roof of your mouth.

Learned that one reading about tantra; supposedly it works by affecting chi flow, or maybe it's just a distracting sensation, but regardless it works for me and keeps me in the moment and attentive to my partner and sensations rather than, basically, dissociating out of the situation with distracting thoughts.