To pardon those absurdities in ourselves which we cannot suffer in others is neither better nor worse than to be more willing to be fools ourselves than to have others so.

The double standard is almost always in your own favour. Your lateness has reasons; theirs is carelessness. Your sharp remark was provoked; theirs revealed character. Running that arrangement means you are, in effect, choosing to stay foolish in exactly the ways you find intolerable elsewhere, because you have exempted yourself from the only correction available.

Take the thing that most irritates you about someone close to you, and look honestly for your own version of it. It is usually there in a slightly different costume. Apply the same standard you were applying to them.