Remember: Someone Will Read This

In team development, someone else reviews your code. Reviewers read commit by commit, trying to understand what you changed and why. A commit that mixes unrelated changes makes the reader's job harder. Clean, focused commits are an act of kindness toward your reviewers.

And there's one more reader you might forget: your future self. Months from now, when you're tracing through the history asking "why did I change this?", a commit with a single clear purpose gives you the answer instantly. A commit stuffed with everything becomes an encrypted message from your past self.