Why do we come to our senses after orgasm?

Hey. When I've reached a state of emotional and then mental relapse, I don't think clearly anymore. I feel dull and start looking for ways to watch porn. I continue like this for a while. After seeing porn once, a setback won't stop me anymore. Even having to stop at the risk of getting caught doesn't get me out of the state I'm in. I'll return to porn and masturbation as soon as I can. Then, sometimes after a long while, I reach orgasm. First I continue masturbating, but then, at the climax, I always stop, suddenly feeling a huge rush of regret and thinking "What?!? What am I doing here? Did I have orgasm again?!?!? "
And at that point I am back to my senses, close all porn tabs and go do something productive, after getting new underwear.
But my question is: Why do we come to our senses at that moment? What is it that stops the entrancement? Why do I not want to continue watching porn and have another orgasm?
I assume it has something to do with biology, but I'd like some explanation.