Doesn't seem to matter who you are, or even what style of shooting you do, most people report that they are really happy with about one in one hundred photographs. This explains why I was so frustrated as a large format shooter as the same odds seemed to apply there - and it would appear they applied to Ansel Adams. Of course, his one was better than our one, but he probably didn't feel any happier with the one than we do.
Common sense would suggest that if you approach each scene methodically and find the absolutely best position and wait for the perfect timing, light and wind, success should be much more common. But, for every picture that you spend 20 minutes (or more) fussing over, you missed 19 other photographs which from my experience quite often turn out better than the one you stopped the car for in the first place.
We will distort the figures if we start shooting 10 images to do a focus blend, 5 images for a stitch, 3 for an exposure blend, etc. but discounting those inflated numbers, the rule is pretty close to right for many of us.
Knowing the odds, we can relax about shooting (it hasn't been one hundred yet so I shouldn't be kicking myself for not getting a great image). In fact, the more desperate we are for a good image, the less open we are to seeing what's interesting in front of us and the more rigid our thinking about what will make a good photograph.
It would be rare to shoot 100 different images at a single scene. I find this takes about three separate scenes. So, if I want to come as close as possible to guaranteeing a decent photo today, I'd better plan on photographing more than one scene/setup. This is relevant in terms of setting up the day, but also in being open to finding something interesting on the way to or from the main work of the day. Some of my best images have been photographed after the light turned bad, while travelling to or from the scene, or from finding something different at the scene from what you expected to photograph.
This willingness to be flexible is crucial to being successful in getting a good image and getting good images is what drives us out there the next time.