I intend to edit this list as I come up with more stuff. Bear with me.
So this can mean clean up your physical workspace, clean up your repository branches, clean up some code you've been meaning to clean up.
This is a great way to fight impostor syndrome, but you shouldn't just read tutorials and watch videos. If you've got a new technology you've been keeping your eye on but haven't had a chance to really dig into, get on it!
mkdir -p ~/projects/someproject && cd ~/projects/someproject && git init
Create shortcuts for yourself
Don't alias something the first time you use it, alias it the third time, and then continually use that alias. This can mean creating Live Templates in PhpStorm, a Bash alias, a Python/Node/PowerShell script, anything. Spend five minutes now to save yourself 30 seconds over the next 12 times you use whatever you use, and you've given yourself back a minute of your life.
If the aliases and other code you create in the course of creating shortcuts for yourself is a real time saver, please, by all means, share it with others. The more we all share with each other, the more time we have back. People creating open source software, even if it's not got a thousand stars on some arbitrary hosting site, they're still heroes. They're giving up their time to save the time and frustrations of others.
There is never a bad time to write good documentation, and this goes for projects that are yours, and projects that you use on a regular basis - if they're open source, contributing good documentation is even more necessary than creating good code, and requires an understanding of what you're writing about nevertheless. Everyone wants to create good code, few create good documentation, and then the code goes unused despite it's high quality because no one takes the time to read code to figure out how it works. Haven't you ever wanted to be the person that "wrote the book" on something?