As to failed paintings, or successful paintings, here is a story from a workshop I took last year. The workshop instructor is internationally known (and an excellent instructor, and great person). The topics of 'when is something done' and 'do you have failed paintings, and how often' came up. He answered the second question by telling a story about one of HIS heroes, another internationally known painter and author of several books with many awards to his credit. Our instructor was at his mentor's house and wound up opening the door (by mistake) that went to his mentor's basement. On the floor of the basement, a foot deep in places, were paintings that his mentor had become frustrated with and heaved down the steps into the basement, where they remained, apparently for posterity. There ensued a discussion about how frequently the older painter had 'bad' paintings, something which my instructor thought almost never happened to his idol. It happened often.
The interesting other point, however, is that the 'failures' lining the basement would be masterpieces to lesser painters and no doubt many clients of the famous painter as well. I've played music for decades now, and it's a similar phenomenon with music and painting I think. The scale of skill in both pursuits is pretty much open-ended. No matter how good you get, there's always someone out there much better, and some that you swear are in a different part of the universe that you'll ever be able to even visit, let alone inhabit. Yet people at that level aren't happy with many of their results either...! So no matter how good you get, your standards rise and there will always be 'failed' paintings. Just this year I pulled out all the paintings I did in the first two years I started painting (in 2008) and threw the vast majority of them in the garbage (kept a few particularly bad ones as well as the 'good' ones for encouragement when comparing them to where I am now). When I first did them, I was pretty proud of a couple of them, never having expected I would be painting and drawing at all. Now, I wouldn't want anyone else to see them.
There is another well-known watercolorist in our area who has been published internationally and has excellent sales of her work. I watched a demo she did and someone asked what percentage of her paintings came out 'good' in her view. She said her ratio is 1:20 - 1 she judges good enough to frame and sell versus 19 that don't cut it. Again, her 'failures' would be prized creations by most of the watercolorists I know.
Interesting commentary on perception and artistic psychology I guess.