Bruce Springsteen - Into the Fire (about 9/11 rescue workers who gave their lives)
Tim McGraw - Don’t Take the Girl
I know there are plenty more, but my brain has taken leave…
Faraway, So Close–Nick Cave
“A Brother Slips Away” by Richard Thompson
“I’ll be seeing you”, as sung by Billie Holiday: - YouTube
Almost anything by Marty Robbins
Gory Glory - the 82nd airborne choir
Puff The Magic Dragon
One of my favourite songs of all time. I prefer the original though. There are lots of live versions out there but this one’s the best.
Within And Without You - Beatles (George Harrison)
Beware of Darkness - George Harrison
Another One Bites The Dust - Queen
A Day In The Life Of A Tree/'Til I Die/Surf’s Up - Beach Boys
Break On Through To The Other Side - the Doors
Dead Flowers - Rolling Stones
Sugar Mountain - Neil Young
Pretty much all of** Townes Van Zandt’s** songs fit this, but* Pancho And Lefty*, Waiting Around To Die, and Marie spring to mind.
There’s plenty of folk songs on this theme. A couple I can think of are Dublin In The Rare Old Times, about an old man looking back at the changes to his city, and how it’s no longer his home, and Killkelly, Ireland, a series of letters from a man to his son as he gets older.
Waiting for the End - Linkin Park
Bowie - Five Years
Ah, if we’re doing “mass mortality” (the world ending, and things like that), how about: “1999” - Prince
“These Days” – Foo Fighters
“Naked As We Came” – Iron and Wine
The greatest song in human history – “Billy, Don’t Be a Hero” 
For time passing faster than you’d like, specifically from a father’s perspective
Don’t Blink (Kenny Chesney) and In Pictures (Alabama).
And could please one of our armchair psychologists explain to me why I always feel vaguely guilty about mentioning country songs here?
Changes- David Bowie
These are the Days of Our Lives- Queen
It’s a Fire- Portishead (that one’s a bit vaguer in what you might be looking for)
If all the songs you mention in a “Songs About…” thread are country songs, you just might be a redneck. [/Jeff Foxworthy]
Who Wants to Live Forever - Queen
Time in a Bottle - Jim Croce