Start Small Every Time
A common theme among side projects seems to be that people become afraid, have doubts, or otherwise become reluctant to release their project until the thing is perfect, complete, and exactly what you envisioned when you had the idea.
I’ve spent my whole career writing software using the agile practice in some flavor. Most of that time has been spent using Kanban and Scrum. Now, I’m likely not very special in that regard - agile is the most popular way to write software in most industries. But my point is that if you’re not at least thinking about your side project like you do your day job when you go to plan or organize it, you’re missing out on channeling such a large part of your work experience.
It’s easy to start small. For me, every idea gets a private GitHub repository. You get a lot of them for free and you can make old ideas public whenever you need room or open the source up when you like.
Once I make this repo, I’ve already checked off a task in the project. It’s like making your bed after you get up. It’s that first accomplishment that moves things forward. Getting this specific step out of the way also saves you time later on because you need a repository for many things these days.
From here, just pick something small in any direction. When you get to the point that it’s useful to do a single thing, ship it. Do something with it. Open source it and write a readme and some docs. Do something with it and I promise you’ll feel so cool even if no one uses it!