A mirror returns a surface without returning the reasons behind an expression.

What a mirror gives you is the outside of a face with none of the history that produced it. The tiredness in it might be a bad night or a long year; the set of the mouth might be concentration or dread, and the glass cannot tell you which. You end up reading yourself the way a stranger would, from evidence alone. That is an unfair way to be assessed by anybody, including yourself.

When a reflection bothers you, name what has actually been happening lately. The face is reporting conditions, and conditions have causes that are usually more forgivable than the verdict you were about to give.