I banged out the first draft in thirty days (350 pages, more or less) and shot it out to a couple of readers, including Eric Patten and my wife Emily (this was before the Story Monkeys formally existed, but Eric and I were already in conversation about writing).
Eric's criticism came back harsh. If I took it seriously, I realized, I would have to do a major rewrite, probably ditching or changing 80% of the first draft. I rationalized, enumerating all the reasons he was wrong.
Then Emily gave me feedback, and her major points were, in different words, the same as Eric's. I lay awake into the wee hours, with my first ever (and, to date, only) migraine headache.
What to do? The answer for me was, and the answer for you will be: move forward. You may have to rewrite your first book, or you may have to ditch it entirely, but you have to get past it. The guy whose first book was his best is like the guy whose glory days were on the high school football team: pathetic.
In my case, I rewrote. It took me three weeks to produce the second draft, which was several orders superior to the first draft, and the process was the steepest learning curve I've ever experienced.