When you look in the mirror, you are seeing a backwards image of your face. This is the image that you are used to seeing and that your brain has become accustomed to. When you look at a photo of yourself, you are seeing what your face looks like to others. This can be a bit jarring and can cause you to feel like you don't look as good as you do in the mirror. Additionally, mirrors show a perfectly symmetrical version of your face, which people tend to find more attractive, while photos show your actual, slightly asymmetrical face. It's important to remember that both the mirror and photos are just one version of how you look and that both have their own unique qualities.