Worst writing advice ever?

Literary agent Nathan Bransford asks an important question: What's the worst writing advice you've ever gotten?

Some of the highlights, from the comments section:
• Remove all your commas. Editors don't like commas and they pull the reader out of the story.
• If it's not coming easily, put it down. You aren't meant to write if you have to try.
• From a creative writing teacher at my first college: "I get one like you in every class. You're a promising writer, but you're wasting your time on genre fiction that'll never be worth anything."
• "War and Peace - now that's a good book. Why don't you write a book like that?"
• "The first page of your novel MUST include the protagonist's sex, age, physical description, and location. Preferably, this is all revealed in the first paragraph."
• Beginners shouldn't start out writing novels.
• Genre fiction is on it's way out, and stories with twist endings won't sell.

I'm not surprised at most of these. I've gotten my fair share of crappy advice. I think one of the challenges of interacting with people during the writing process is that you need to learn to filter the notes and feedback you get. It's something the Leaguers discuss with regularity. Only you really know what you want to accomplish with your work, and only you can decide which pieces of advice will really help move your work forward. You have to also realize that the people reading your work don't have the notes, background info and/or mental cues that you've created while working on your screenplay/story/novel. That's a plus and minus. The plus is, they're looking at it as a normal reader would, so their reaction is much more natural and in tune with how Joe Reader would react when picking up your book off the shelf. The minus is, since the book isn't finished, they're going to have questions about where it's going or what certain things mean. Questions you've probably already answered internally. Still, overall, the good outweighs the bad, as long as your confident in your peers.

One of the biggest benefits of the League, I've found, is that we're a group of competent writers all coming from different directions. So, when I bring something up for comments, I'm getting a wide array of feedback from six very different people. If you believe in the skills of the people you're handing your work to, then you've cut down on the advice filtering process.

What's the worst writing advice you've ever gotten? The best?

[Via Jacket Copy]