Ask HN: How to get motivation of side projects if you don't need the money?

I have a really good salary as a remote engineer (and I live in a part of the world where one salary could last me 6 months). However, I am getting bored of my work (due to many reasons; AI could be one of them).

I want to try different side projects (not all of them being tech-related); for example, opening an online niche bookshop would be ideal. But when I consider the effort I would have to put in and the money I would earn (a small percentage of my salary), I know it's not worth it. It will add stress, consume time, and it won't a good experience anymore. I am also aware that creating a side project that will give me a significant portion of my salary is almost impossible at this point.

I know some people say that we should do some things just for the pleasure of it and not for the money, and I agree, but that's only when money is not involved. How can you do it with side projects / side businesses?