As someone who has been failing on side projects for over 20 years, I feel qualified to answer this question.

  - Have one private repository for random projects
  - Work in private repositories for random 
    projects that progress.
  - Move to public repositories when the project
    gets somewhere.

These tips above make failure cheap. Success is built on the many failures.

I also have general tips on side projects that make them more fun and less like work:

  - Use a different editor/ide to $job.
  - Use a different programming language.

I also have these general tips based on mistakes I made in the past:

  - Read other peoples solutions on github. Its inspiring.
  - If you get stuck take a break. Its not work and you can slack.