We all need side-projects, it's how we build skills, and thus, how we grow. By definition, a project is time-bound: the quicker you make progress, the higher the probability you'll deliver.
Launching a project's deliverable is hard. Easier than ensuring the actual success of the outcome, but still full of obstacles.
It took me six months to deliver my first project - a server monitoring product. The second one, a conversational chatbot, took six months as well. My third product, three months. My fourth, one month. Then came 200 Words a Day, released as a minimum viable product in two days. Testimonials Wall took a week.
My time-to-delivery considerably decreased over the months, and the most successful product I ever made took the least amount of time to launch. The quicker you launch, the better.
There is no hidden secret: if you want to finish something of a significant size, work on it a bit every day. Launch deliverables as early as possible to get real-life feedback.
Even when you're not motivated or you don't feel like you have time, find a little something to do. There is always a 5-minute task to get done. Even if it ain't much, you showed up. You earned the right to call it a day.
It's not about how much you do, it's about consistency. These days, I'm working on four projects at the same time. Doing one little thing every day is definitely how I'm gonna pull it off.