Killing the bad stuff, he says, is just as important as doing good stuff. I agree -- "quitting" is awfully stigmatized, but sometimes it's the right course. Sometimes your work is bad, and you're just wasting time pounding your head against its ugly hide.
However. As someone points out in the Lifehacker comments, giving up too soon really is a bigger problem for most artists. The trick is knowing what's worth finishing and what isn't. Ira Glass doesn't have to worry about that. It's not hard to tell when a radio story put together by a group of people isn't working. It's much harder to know when it's the novel you've been working on alone for five years. And sometimes you have to finish a thing before its true crappiness -- or greatness -- comes out.
And sometimes the crappiness of a project doesn't even matter. It's just the thing you have to do right now, and so you do it.
How do you know if your work is worth finishing?