I came across this quotation from Becoming Real, by Steven James. I haven't seen the book and can't vouch for it, but I find the following to be well-expressed:
Everyone dies in the midst of something. People die in the midst of going to the dentist's office or driving home from vacation or taking a shower or watching TV or mowing the lawn or barbequing ribs on the back deck or enjoying a good night's sleep. People die in the midst of arguments, grudges, dreams, plans, careers, headaches, heartaches, and courtships. People die in the midst of marriage and puberty and old age. Some die in the midst of being born. Or even before that.
We all die. And we don't die when we expect to die or after our dreams have all come true or when we've finally made it in the world. No, most of us die in the midst of pretending we'll never die. We die living as if tomorrow were guaranteed and this life will last forever.
When death stalks us or claims a close relative or friend, we weep in shock. How could this happen? It's so out of the blue! Death is never out of the blue. It's always there, right before our eyes. And soon after the tragedy, we go right back to living as if each moment didn't count for eternity.
Life is a gift. Death is a certainty. Dying is one thing we're all capable of, one thing we all ultimately succeed at.
I've often heard people say things like, you've got your whole life in front of you! That's simply not true. We don't have our whole lives ahead of us. We have our whole lives behind us. What we have in front of us is a mystery that could be over at any moment.
*Memento Mori is a Latin phrase meaning, "Remember that you will die."
(I took the top photo at a cemetery in a Naples convent; the one below is from a floor tombstone in a church in Malta.)