I'm quiting writing forever because:

A. My writings are still basically the same since when I started. I must not be a real artist, because I haven't been able to change at all. Or I don't suffer from the common artist's delusion that my work is improving (Nor will I fool myself into believing that changes to the shadow alter the substance). I recall fondly (as Red Sox fans recall misfortune falling upon the Yankees) when Eric Clapton said something to the effect, "I wouldn't keep on making music if I didn't feel I was getting better." What a delusional nitwit his best work was almost 40 years ago. I enjoyed his self deception because I knew the truth, I had a hold upon the facts: his music has deteriorated consistently since his heyday, like every artist--they lose their edge, it's hard to quantify but it's true, fact. Listen to the rabble that Sting puts out today and you'll get my idea.

B. I'm out of ideas, and I can't replicate or fabricate the lifelike intricacies and innuendo that assert itself to any conscious human being. Comedy pervades reality but eludes writing.

C. Star Crossed Navel Gazing. I'm simply not smug enough to continue.

D. The thrill is gone. It's no longer fulfilling as a job-well-done. No matter how hard I work, which isn't all that hard, it's never going to be any good. My poor ability to pay attention has thwarted another endeavor.

from rotten.com
Robert E. Howard (1906-1936)

Credited with the creation of a literary sub-genre known as "Sword and Sorcery." Became a writer so he could be his own boss. With respect to his aversion to traditional employment, he once remarked, "my passion for freedom is almost an obsession. Writing has always been a means to an end I hoped to achieve. Personal liberty may be a phantom, but I hardly think anybody would deny that there is more freedom in writing than there is in slaving in an iron foundry, or working - as I have worked - from 12 to 14 hours, seven days a week, behind a soda fountain. I have worked as much as 18 hours a day at my typewriter, but it was work of my own choosing." A life-long sufferer of bipolar disorder, Howard grew increasingly morose in the late 1920's. He told his friends only the prospect of his mother's grief kept him from committing suicide. When she finally died, he climbed into his 1935 Chevy and took his life with a borrowed pistol.

"I don't believe that people should take their own lives without deep and thoughtful reflection over a considerable period of time."