My $.02 (because that's all it's worth... if that!)...
When I'm out just shooting for the sake of practice, I don't count shots, I chimp, I evaluate what I'm doing, and take note of lighting/settings/composition, etc. in order to learn what I'm doing. Most of these shots never even are downloaded and/or deleted. They are there for the sake of my own learning. They aren't terrible - but they are like the pain pill example... what am I going to do with them later?
When I'm shooting personal work, I have about a 95% keeper rate. I shoot, I chimp to make sure I like what I took and make adjustments or move on. It's not perfect - I don't really care if it is or isn't - because these are MY pictures for MY memories. Our last vacation, we were there for 12 days and I took about 850 photographs. About 700 will make it into my album when I finish editing. Some are blurry... some have bad color... some are super cool and some are freaking awesome. But, I don't let it get me down and I sure didn't have to par down a bunch of duplicates either.
When I'm shooting client work, I have about an 80% keeper rate, and out of those, I usually have 1 or 2 that I consider portfolio work (work that I deem good enough to represent my company). I don't chimp often, I know my settings and my lighting. I rarely don't keep a photo due to an exposure issue, but more likely eyes closed, and less than pleasing expression on a clients face, or a composition that I tried that didn't work, or a test shot when using off-camera lighting.
I think what distinguishes a fairly accomplished photographer is consistency. We know what will and won't make a good shot, and we make adjustments on the fly to compensate. Sure I can take 700 shots and 80% will be keepers, while you may take 700 with only 1 being a keeper.
But the only way to get there is through learning, practice, research, practice, trail and error, and practice.

Don't EVER stop practicing!! I shoot every day. Most of the time it's nothing that I'm shooting, but I practice all the time, which when I'm in a high-pressure situation, I'm golden.
