I've been idly wondering what exactly could have caused an ex to lose interest suddenly... not easy to pinpoint considering even he didn't seem to know (if there was a single causation... I always assumed it was multiple factors)... but, one major thing that seemed to happen in the few months prior was him getting really frustrated over seemingly minor things and reacting by smashing his head in doors e.g. (was supposed to have had AS too, so I assumed that was the habit he developed over the years, although I physically tried to stop it usually)... e.g. when we went out once and many things going wrong, until finally he couldn't seem to handle it anymore when I said satirically that I didn't want to go out again out of frustration with the outside world... I obviously meant it in more humour than he took it.
Something else that was more directly perceptibly frustrating to him was the fact I couldn't run as fast as him (his stamina was above average, whereas mine is below, so...) - so when we occasionally went out and wanted to go faster than usual he'd run whilst I cycled...
One other thing that also seemed to terminally frustrate him is when I didn't want to open the door to a room because I was feeling anxious, and then getting minorly angry when he tried to open it with a roundabout way... as usual, though, he probably took it far more seriously than I did.
So... was this anything I could have avoided? Or was it inevitable due to some innate ennui? I'd just... like to know in case I can avoid it next time, of course, although considering life is chaotic and factors variables, I suppose it's not likely to be a singular cause...