This is a dilemma of lots of people who shoot professionally - they have photos that they want to keep because of the subjects/moments/memories which are objectively not as good as the photos that could take with the same subjects/moments/memories if they had approached them more as the professional shoots -- they did not.
The solution to that is simple - two different collections. One for the 'Personal photos' and one for 'Excellent Photos'.
> It's annoying as I love it, and I love going out and practicing more. I've read lots on composition etc and how to use my camera but I find it so hard to actually picture the scene in my head and what will make a good photo
Never take one photo. In fact, never take two or three photos. Take dozens photos even if you are just tapping a button on your phone camera app. Move phone left. Move it right. Change angle. Move closer. Move out. But keep pushing the button. After that pull the photos for the same scene into a strip and do an edit. First cull obviously bad photos - out of focus, washed out background if you did not want it, weird dude sucking on his thumb in a corner etc -- you took a dozen photos of nearly the same scene so it is not like you don't have a room to cut. After that do a tennis tournament. Compare two photos side by side. Pick a dinner. Delete the loser. Walk this down to 1 photo for that scene and be amazed at how much better that photos is than the one you thought you were going to get.
> Also, what are peoples throw away rates like? If I go out for a day with the camera and take say 20 photos. I might save 1.
If you have people in the photos, then keeping one in twenty for a day of shooting is a very high and unnecessary precious keep rate ( please don't take it the wrong way ).