It would be unusual to see an epitaph containing any personal thoughts, because most such messages are written by surviving family members, not the deceased.
Yeah, there's typically little or nothing. No meaningful sentiments from the deceased. That's part of what the popular funeral poem "The Dash" plays on—everything that mattered in a life, by the time it's nothing but marks on a stone, is expressed in the distinctly inexpressive dash between the birth and death dates. It's rare to actually put anything about the life on there. "Loving father" or something is usually the most you get, if that. Sometimes poets or writers will compose a stanza for theirs, but those are exceptional.
There was a famous Swedish author called Fritiof Nilsson Piraten, whose grave lacks any name but instead had the inscription (translated):
"Here below are the ashes of a man who had the habit of putting everything off until tomorrow. But in his last days he improved, and did actually die on January 31, 1972."
One in Tombstone, AZ (probably the only place people read these) says "We killed him by mistake. Too bad."
There may really be a grave with the poem: "Here lies the body of Richard Weigh, who died defending his right of way. He was right, dead right, as he sped along. And he's just as dead as if he was wrong"
There's a great song by Titãs, Epitáfio, which imagines a gravestone with all these thoughts, "I wish I had watched more sunsets, I wish I had cared less..."
I wish I was a baller
I wish I had a girl who looked good, I would call her
I wish I had a rabbit in a hat with a bat, And a six four Impala