I can totally relate to this!!

I will be doing fine and then I see myself in a mirror and it really catches me off guard. I will shut down because the person I felt like I was will suddenly seem like some weird persona that doesn't align with my image, and I'm just not sure how I should be behaving anymore.

I suspect it may be to do with the fact that my self image hasn't changed since I was much younger; possibly because since then I have not really been that happy, so I keep my old self image out of preference. When I see myself in the mirror it 'looks wrong' because it's simply not the persona I'm expecting to see. That's just a guess though.