A mirror shows who you want to see. A video shows who everyone else sees. Watch the video.

Looking at yourself, you adjust. You hold the pose you like, you smile at the moment you planned, you see the version you were going for. Recorded, none of that help is available, and you get the habits you never noticed: the filler words, the shrug, the way you cut people off. Uncomfortable is usually the sound of new information.

If there is something you want to get better at, film thirty seconds of yourself doing it. Watch once for what works and once for one thing to change. This is about how you come across, not how you look, so pick a note you can practice.