Small commits
Every word of this post was written by a person.
A commit is a point you can return to. Hours of uncommitted work is hours you cannot get back if the next command goes wrong.
One logical change
If the message needs the word "and", it is two commits. A reviewer can hold one idea in their head; a reverter can remove one idea without collateral.
Commit before the risky step
About to run a script over two hundred files? Commit first. Recovering from a bad sweep is a one-line git revert — if the good state was committed.