The critical thing about a first draft doesn’t have much to do with how smooth the prose is. What it does is allow you to find out whether all the pieces fit. Whether the characters work, and the logic makes sense.
Later, he points out a second problem that writers sometimes run into:
Sometimes there are aspects of a project that can’t be checked out in advance. You simply have to sit down, do the writing, and leave yourself open to whatever judgment shows up.
In his post, Jack provides real examples of how these two things have impacted his own work. It is a fascinating peek into the way a writer works. Go check it out. And be sure to read through to the end. There is some interesting Alex Benedict news, if you pay attention.