>How do you find one?

You don't find one, you create one. Instead of forming cool short projects, form a long one. Just as an example, lets take running (since you mentioned it). Instead setting a goal like "I want to run 2 miles three times a week", make a goal like "I want to run a marathon by August 2023." Then setup a plan to make that happen, build up each week until you can run longer and longer distances.

Also, realize that focusing on one project will necessarily mean not focusing on most other projects.

> How do you find one?

Find an itch, and scratch it. Find something that gratifies your creative urges. This could be anything. For me it's mostly computer related things. I have several private side projects that I hack away on in my free time, and have no plans to publish them on GitHub just for validation and praise. Although I'm not ruling out releasing it publicly. If the project could help more people other than just me, it could be time to host it publicly it on GitHub.

Thank you! I’ve decided to start and write a blog, and I’ve just published my first essay. I’m writing a lot to myself, and long form essays are thought provoking and interesting, so I’m doing it!