For me it was the acceptance that death is closer than I would like to think (i.e. It can happen easily and quickly without any kind of accident and the chances

For me it was the acceptance that death is closer than I would like to think (i.e. It can happen easily and quickly without any kind of accident and the chances of it happening before I live as much as I've already lived are pretty high) that kicked in, not the realization it's inevitable.