If one could predict which images will turn out to be 'keepers', if we could tell beforehand what images others will like, life and photography would be so much simpler, but perhaps not quite as interesting. I have a reasonable idea of what people will like and certainly once I have edited the image, I generally know if this is going to be something I like long term (though not always). As to seeing something and predicting before even capturing the image whether it's going to be good or not, I'm downright terrible at it.
So it would seem that despite writing about composition and what photographs well and what great photographs tend to have in common, I'm still not good at prognosticating what images are going to be hits with other people.
The implication is that if something caught your eye and if it doesn't have any fatal irredemable flaws, you might as well go ahead and finish photographing it, because you might be surprised, the image you doubted may become your signature image.