I think the problem here is that your side projects aren't really that fun.

It's not that fun to read a complicated, dense book.

It's not that fun to learn a language, in fact it's one of the hardest things for your brain.

It's not that fun to make a personal web site that's basically going to end up being a LinkedIn profile.

For me, I do have a side hobby. I built a tool to make grids of peoples' photos into posters that I sell on Etsy, things like people's photos of them visiting each national park. It's a weird hobby but the fact that I'm actually selling something was a big motivator for me. I love making sales -- even though I've done less than $100 total so far.