Kol, same here.
Also remember that mirrors probably don't reflect light as well as you would appear through just air. And the lighting in your bathroom is probably much more soft and yellow than the light sources in other places. It's probably not just your voice - you probably also look much more terrible than you imagine.
And smell. You probably get used to your own smell, but to others it may stand out in sharp and stinking contrast even the few moments where you forget to think about it.
I hope this enlightened you all with more objective and realistic views of yourself.