Have you considered that maybe you simply aren't as interested in the things you want to accomplish as you think you are? I ask because I struggle with the same thing and that question is really what I'm asking myself now too. I'm a mechanical engineer and I generally like building and designing things...to a point. I enjoy it at work but by the end of the day, I just don't have the motivation to keep trying to build things even if I'm superficially interested in it at a high level. I'm probably just not as into as I thought I was. At least not enough to do it at work and then at home.