One option is to always have a few different projects going to keep your perspective fresh:

Create commits and PRs as if you were on a team, then go work on another project. Then come back and re-read your own PR. Having been doing something else for a while, you'll see it with fresher eyes. If it still makes sense and looks good, ship it.

This won't catch everything - you probably still have blind spots in your skill set. We all do. But it will prevent tunnel vision from being too close to your own code.