For all sorts of improbably evolutionary reasons, when you're young you think you're a little bit invincible. Rocks will bounce off you. Of course you could hold that collapsing roof up. This flesh is flame-retardant.
Even as a slightly neurotic young chap, I was still quite firm in the belief that if the house was falling down, I'd still have enough time to grab a few of my favourite things before evacuating. I'd probably still grab my bag before leaving the craft, contrary to all sound advice. Of course a car crashing into me wouldn't break anything. I suppose if I didn't I probably wouldn't have left the house very much (thus, of course, contrarily putting myself in more danger).
Watching some of the footage from Japan makes me realise my point of view has changed. I'm a bit older now. I would just grab my loved ones and run and run and run and not stop to look back.