I know exactly why I "didn't progress" and they did, as you kind of put it.. I decided not to. They decided to continue. I stopped training, they didn't. When I was still active I progressed same as they did - and I saw nothing super-human in their later performance. Obviously I only have intimate knowledge about my own field, I know nothing about e.g. 100m sprinters, jumpers and the like. And, as everybody else, I'm pretty suspicious about pure muscle-based sports like weight lifting.