This is my take on it: when you start something it's at first easy and then it gets really hard. Or boring. Or you get distracted or disenchanted. But if you stick with it long enough you eventually become an expert in the space (or what you are building becomes good enough) that it's not state of the art. And then you can innovate on it or sell it or sell your skills. But you have to get through that tough valley in the middle.