The higher you go, the farther you can potentially fall.
I think that the majority of it is definitely psychological - just that lack of feeling augmented beyond your normal capabilities. When coming off cycle and even long after PCT is over, training in the gym does become a mundane thing for me. You need to learn to make it interesting and teach yourself that its not all about being 'ON'. I personally have never had a post-cycle crash. The only thing that happens is I just feel a bit dissapointed that my cycle (like all great things) had to come to its scheduled end, and that I know i'd no longer be able to make the vast leaps in progress until my next cycle down the road. I never found the coming-off period any worse between when I use things like test or a cycle that has tren.