I think the problem is that what you want to learn is not always fun all the time. At some point you'll hit the wall and you have to overcome it (I admit, however, it never happened to me in programming, but for example I hate driving while I have to get better at it). It's tempting to make an excuse like you're simply "not built for it" - so that you can give up without feeling bad. That is a harm of the fixed mindset as far as I understand. I'm not saying that people should feel bad all the time, but the "nature" excuse is sometimes a slippery slope.