He just refused to do the rational thing and quit. In a longer piece, well worth reading in toto, Brain Pickings describes how best-selling author Michael Lewis (barely) got his start in writing:
Even though his thesis adviser at Princeton praised the intellectual angle of his senior thesis but admonished him to never attempt making a living with that kind of writing, Lewis was drawn to the writing life. He wrote a piece on the homeless and pitched it to various magazines. It was rejected, with one magazine editor noting that “pieces on the life of the underclass in America” were unsuitable for publication.… Still, he “kept plugging away” and, in 1983, applied for an internship as a science writer at the Economist. He recalls:
I didn’t get the job – the other two applicants were doing their PhDs in physics and biology, and I’d flunked the one science class I took in college – but the editor who interviewed me said, “You’re a fraud, but you’re a very good fraud. Go write anything you want for the magazine, except science.” They published the first words I ever got into print. They paid ninety bucks per piece. It cost money to write for the Economist. I didn’t know how I was ever going to make a living at writing, but I felt encouraged. Luckily, I was delusional. I didn’t know that I didn’t have much of an audience, so I kept doing it.
Lewis’s first few years went much like most freelancers:
Before I wrote my first book in 1989, the sum total of my earnings as a writer, over four years of freelancing, was about three thousand bucks. So it did appear to be financial suicide when I quit my job at Salomon Brothers – where I’d been working for a couple of years, and where I’d just gotten a bonus of $225,000, which they promised they’d double the following year—to take a $40,000 book advance for a book that took a year and a half to write.
My father thought I was crazy. I was twenty-seven years old, and they were throwing all this money at me, and it was going to be an easy career. He said, “Do it another ten years, then you can be a writer.” But I looked around at the people on Wall Street who were ten years older than me, and I didn’t see anyone who could have left. You get trapped by the money. Something dies inside. It’s very hard to preserve the quality in a kid that makes him jump out of a high-paying job to go write a book.
Which shows yet again that quite often, successful writers are the ones who don’t give up — and that preserve that kid-like quality of persisting at something that is pretty much hopeless.