Robbie, it's called the evolution of ageing (coming from a 53, ER sorry 35 year old! Lol). Without a doubt, the knowledge and experience of possible repercussions impact your riding, often in subtle ways. For me it's absolutely only a mental thing: if Greg can pin downhill at those speeds at his "age" (aside from training, skill, technique and talent), then we can all attain/keep our own unique speeds up. It's all about mental approach, assuming skill, training and physical form is still on same par as before.
So for me, it just takes a small sandcorn moment of doubt, loss of positiveness or confidence, worrying about crashing etc, which will possibly have immediate or delayed consequences.
Case in point is my own last ride down Cobra: I have been working with a lady friend who is prepping for Epic. She has progressed a lot but she fears that stony, jutted rock garden section and has fallen hard there. She walks it now. But having dealt with this situation with her a number of times, somehow planted a small seed with me. And promptly I had my very first small off there. It took just a small moment of hesitation and a fleeting thought of falling there......and presto.
Anyway, that's what it seems it is to me. Aside from all technical (incl tyre pressures etc) and physical aspects being equal....which strictly speaking they never really are, but hopefully you get what I mean.
Good luck with your journey and evolution 😁
