Most living writers will tell you to complete a full first draft before reworking anything, but I'm incapable. I always worry over the first stretch, scrapping an entire book's worth of first scenes before I find an acceptable point of entry. By now, I'm in no hurry. This sucker will gel when it gels. I've learned to enjoy the delays.
... I used to bemoan the months-long wait between polishing a piece and learning whether it was rejected or accepted. These days I'm happy to have the time to cool off, because the work my brain does when I'm not watching it is far more impressive than the stuff it comes up with on demand.
That sounded familiar, I thought. Then I realized, this scrap-the-start business was precisely how I threw myself at Flight of the Vajra. It took almost twelve years from the original idea — which, in the end, didn't resemble the completed product in the slightest — before I could even start writing it. And when I did start writing it, I went though (as Gabe put it) a whole book's worth of first scenes before finally finding the groove.
One of the foundational lessons of The Mythical Man-Month is that the first iteration of anything is a disposable one. Nobody gets it right the first time, because the point of the first time isn't to get it right — it's to get something, and then to move that into the right direction. You always throw the first version away. This doesn't mean a good part of what arrived with the first version can't be re-used, but staying married to it ("kill your darlings!") is unwise.
Students of Buddhism ought to be familiar with the idea of the teachings as a raft, something you use to reach the other shore and not cling to for their own sake. Likewise, the first iteration of anything is not a thing in itself — it's a ladder you use to climb to the previously inaccessible higher floors of the Tower of Babel you're trying to climb.
But the other mistake is to assume that the next one is somehow the real one. The future work is no more a final destination than that first draft. It exists less as a thing unto itself than it does as part of a conversation between you and the rest of creation. You just gotta keep the conversation going, somewhichway.