Originally Posted by CurrentlySober

Thats because when you look in the mirror, you are seeing yourself in reverse - a 'mirror image'

Because that is the main everyday reference you have regarding what you look like, your brains 'sense of self' accepts the reverse image as gospel...

So when you see yourself in a selfie or other photo, you don't look 'right' because subconsciously your brain expects you to be a mirror image.