Tricky advice there from Kurt Vonnegut, author of "Slaughterhouse 5" and many other books. They did get edgier and stranger as he went on but he never went over. Some writers have, of course, both with their writing and in their lives.
If you've never read "Slaughterhouse 5" you may not know that's its the story of a young American soldier, Billy Pilgrim. He's taken prisoner by the Germans in World War II and housed, along with his fellow prisoners, in a disused slaughterhouse in Dresden.
When the Allied forces destory the city with massive numbers of bombs, the resulting firestorm wipes out most of the city's population. Billy and the other captives come up to the surface to see a scene of unbelievable devastation.
All that happened to Kurt Vonnegut.
He pushed the novel version of it farther, having Billy randomly re-live parts of his life and also his death. He introduces The Tralfamadorians, aliens who kidnap Billy and put him on show in their zoo, as well as Howard W. Campbell Jr., a real-life American Nazi, and even himself when he starts the book by writing about his own experiences and why he wrote it.
In 1958, when Vonnegut was 36, his brother-in-law was killed in a rail crash two days before his wife, Vonnegut's sister, died of cancer. Vonnegut adopted three of their children.
Perhaps when you have seen, as Vonnegut described it, "carnage unfathonable," and been sorely tested even afterward, you find yourself stranded on the edge.
At any rate, it's where some of the most interesting writing comes from.
I've generally tried to avoid it but found that when you do that, it comes to you. Better to embrace it and turn it into something useful.
Where is your edge?
Are you close enough to it?
Too close?
Or, I hope, just right?
(If you'd like to learn to write from the best, get a copy of my new book, "Your Creative Writing Masterclass." It features writing advice from more than 100 classic and modern writers, plus my guidance on how to apply that advice to you want to write. It's published by Nicholas Brealey and you can get it from Amazon or your other favorite book seller.)