You are not looking at yourself. You are looking at yourself from about a hundred-millionth of a second ago, which is how long the light took to leave your face, strike the silver, and return. Every mirror is a tiny time machine, and it always shows you the past.
Consider what is actually happening at that shining surface. The glass is nearly irrelevant; the work is done by an atom-thin coat of aluminum behind it, a sheet of metal maybe a hundred atoms deep. Light arrives as a swarm of photons, and the loose sea of electrons in that metal will not tolerate an electric field inside itself, so it wobbles in perfect opposition and flings the photons back out at exactly the angle they came in.
Angle in equals angle out, enforced photon by photon, billions of times, with no committee and no delay. That is why your reflection is sharp and not a smear. The metal is not showing you a picture. It is refusing to absorb one, and the refusal is so orderly that it reassembles your entire face in flight.
It reverses front to back, not left to right, though people argue about this endlessly. The mirror does not know which of your sides you have named "left."
And the aluminum itself: forged in the cores of dying stars, flung out in a supernova, folded into a rock, dug up, purified, and vaporized onto glass so that a swarm of photons carrying your face could bounce off ancient stellar ash and come home to your eye. You lean in to check your teeth.
You are using the exploded guts of a star as a clock accurate to the nanosecond, and it is telling you, faithfully, what you looked like a moment before you existed.