According to him (and I agree completely) the secret to being more successful as a writer is as simple as can be:
WRITE MORE, DO OTHER STUFF LESS.
That's it. Everything else is meaningless. You can take all the classes in the world and read every book on the craft out there, but at the end of the day, writing is sorta like dieting. There are plenty of stupid fads out there and charlatans promising quick fixes, but if you want to lose weight, you have to exercise more and eat less. Period. Every writer has 10,000 pages of shit in them, and the only way your writing is going to be any good at all is to work hard and hit 10,001.
He also said that writers block was just another word for video games.
I found this piece of advice a long time ago and I've had it tucked away. Since then I've all but given up video games and I can vouch for the efficacy of the advice. Though his metaphor about eating less and exercising more rings a little hollow after all of those years working on Killer at Large. Obesity is WAY more complicated than writing.