I've been in a very similar situation, and still technically don't have proof that I've left it. When I first started writing, I'd read probably a dozen books on how to write. I'm super analytical about this sort of thing, and went into it well prepared.
I was awful anyway.
My first story attempts never even made it past a few pages. I'd start writing and would quickly realize that nothing coming out of the fingertips was the slightest bit fit for human consumption. NOT the cat's pajamas, if you take my meaning. However (queue music indicative of sage advice), the important thing isn't how far you get, it's what you take away from it. I sat down and analyzed each and every one of those failed starts to figure out
why they were so awful. Short answer: I had rushed into the story too fast without establishing setting, characters, or even mood.
Armed with this realization, I went back and planned my opening scene ahead of time, wrote some more, and joy and rapture, got several chapters in.
Nope. Still lousy.
So I once more analyzed the problems. When once I figured it out (in this case, it was the reverse problem; I got three chapters in without even clearly establishing what the conflict of the story was going to be), I planned some more and went back to square one.
The point of this long, boring story (thanks for humoring me) is that by this time I've scrapped almost a dozen stories, two of which had broken 60K words. But I'm not in the least discouraged, because in each case, I was able to figure out precisely and definitely
why I scrapped them. I was then able to avoid that pitfall in the next version by restructuring and replotting portions, trimming away dead weight, streamlining the introduction of new material, creating conflict where previously there was none, and generally doing all the things that I
should have done before I started. Each draft is longer than the last, and I rarely make the same type of mistake twice (at least, the glaringly obvious kind that's draft-scrap-worthy; I repeat the humbler kind at least thirty-seven times a day
)
So I guess my advice for you is to look at each draft and figure out what is wrong with it and why you scrapped it. Was it because of lack of conflict/tension? I had to scrap a 40K draft because I discovered that after my first chapter, I didn't have a single scene that could be described, even charitably, as moderately gripping. Is it because of a lack of information? I once had a draft where nothing remotely interesting was happening to the main character, and I realized it was because he had no clue what was going on, and therefore wasn't really a participant in the struggle. Is it lack of direction? Do you have enough characters to make your setting feel like it's full of people? Is your story hanging in a vacuum? There's any number of things that can go wrong with a story, and though I've learned to recognize a few, I am quite confident that I'm going to continue smacking up against more of them in the future.
As a final anecdote (yes, sorry, I'm far to ready to share those), I am currently outlining my story all over again before taking the plunge. Eventually, it will be a scene-by-scene outline, although at the moment it's a good deal more general. As I was looking at it, I realized that there was a large section of the book that had no purpose. My characters were traveling from point A to point B. I couldn't really just skip over that part, since it was through enemy territory, and it wouldn't make any sense for nothing to happen (not to mention it would severely damage the reader's view of my villains), so I'd just thrown in some random action/adventure. But in the grand scheme of things, none of that mattered to anything. If I had dispensed with outlining and begun writing, I can tell you exactly what would have happened: I'd have gotten up to this point and then stuck. After muddling around for a while getting nowhere, I would have scrapped the draft, analyzed my mistake, and
then set about fixing it. Thank God for outlines!
[if you're curious, the final solution ended up involving the creation of a new character, modifications of all previous sections to incorporate the arrival, the relocation of a pivotal, pre-existing character, and a slow build-up to a mini-climax where one of the characters loses something extremely important. This section now has a solid reason for being in the book, and I anticipate no problems when I finally get round to writing it.]
TL:DR; Figure out why you scrap your drafts and outline sufficiently to avoid making the same category of mistake all over again is my advice.