Knowing when to quit is an important skill. Sounds like you went a bit to far but you survived so no real harm done. One of the MM performances I am most proud of was when I turned back when it just got too wild.
I would typically go to a MM with a choice of 3 cagoules available. The light one I did not expect to wear much. The heavier weight one I would take if I expected to have it on all day long and the full on hurricane conditions one which I only ever used the once.
The classic LDMT story is of course the year when there were 2 finishers and the winner had supplemented his kit with a bin bag to very good effect.
In future I will always be taking a survival bag and an extra layer - surprised these aren't mandatory. But I let the required kit, and what everyone else was carrying, overrule my sound mountain judgement.
It's only the second time I've been genuinely afraid of actual death, the first being on Four Fans where I was swept away by the river and had to drag myself out after desperately clutching onto a rock. I learnt that lesson - I am extremely careful crossing rivers now - so maybe it was time for me learn this one too.