When I started my career in the mid-90s, I thought I'd try to learn everything there is to know about Windows development. It didn't take too long before I smartened up and realized it's an impossible task as the goalposts keep moving. Today with web development, and multiplatform targets, it's even worse - much worse. My approach these days is, learn what's directly applicable to what you're developing, and don't worry about the rest. But I still burned out. I still love to code, but it's been years since I wrote any hobby type of side-project for myself in my own time that's anything above the scale of "small utility".