This is a bummer because I have multiple app/script ideas I'd love to work on which have been sitting in the back of my brain for months at this point.
I could have a second cup of coffee to keep me going, but at a certain point I'm just wired and fried vs fried and not wired, and my sleep can be affected when I do this.
I sleep well, I run in the mornings, sometimes lift weights later in the day, eat well, and have a decent enough social life. I'm not depressed by any measure, just exhausted from the work day.
How do I summon the mental clarity and energy to pursue my hobbies after a long day of work?
One trick is to identify skills that will help you build the apps/scripts that you want to build for yourself, think of a way to apply those skills that benefit your work, and justify learning them on the job that way. This makes it a win-win for both you and your employer.