The Boy Scouts and many outdoorsmen/women have a code of leaving the campsite better than you found it. That means picking up trash even if you didn’t leave it. When you finish your stay the campsite should be pristine.
That guideline can easily be translated to software development. I highly doubt you’ve opened up a class file and, besides the big issue went in to fix, you thought there was nothing you could do to improve it.
Does the formatting conform to your team’s standards?
Do all of the variable and method names make sense?
Could any part of the code be made less ambiguous?
Next time you hop into some code for a “quick-fix”, take a look around and see what you can do to leave the file better than you found it.