Extinction-level event

The person I see now is not the same person I've met many years ago. I know - everybody changes all the time. There is a difference, however, between changing by natural evolution and changing by sudden destruction - and you did not naturally evolve from what you were into what you are now. Or rather, you did naturally evolve into what you are now, but such evolution is so extraordinary and unlikely that it becomes implausible. What happened was not evolution but an extinction-level event, a massive catastrophe that wrecked your old self and brought to life a person bears your face but not everything else that defined you.