If you're putting 100% of your energy into your day job such that you're exhausted at the end of every day, you might want to tone it down a little. I'm not saying to become a do-the-minimum slacker, as some might, but you do need to keep some capability in reserve for a crisis.

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.