This is more related to lighting than to mirrors, but the worst thing for me:
Lovely summers day, can't wait to see my friends outside! Sun is shining for once in Ireland! Which everyone loves right? Oh but I forgot (and somehow, I do actually forget still) that I'm thinning badly right the way up to the crown, and anyone who catches a glimpse of my head from an above angle will not believe how bad it is.
My hair has thickened up a bit so it's at least passably not bald any more, but for a few years it was so thin from that above angle, with sunlight directly down on it. Especially bad as we often have picnics and things sitting on blankets in the grass, and sometimes people would be standing up talking, and they'd notice. And in a funny way you get a sense of who's going to be a complete a**h** when they do notice, you know that the nicer people will see it initially, probably glance again, maybe once or twice, and the worst assholes will notice, stare for 30 seconds, look away briefly, stare, and this can go on, and you can even tell by how they aren't focussing on their own speech patterns that they're completely distracted and refuse to be otherwise. And you can even wipe the top of your head, ruffle your hair, as a sign that you know they're looking, and one time I even looked up at a guy, pissed off, and he just asked me with a big friendly smile if I was OK, while still staring at it!
OK but this is another example of how I let it affect me more than I should have, I became self conscious every time anyone stood up or a standing person approached us, I did get paranoid and got it in my brain that people were looking for that angle. On some occasions people may have only looked once, but in my head, I'd still be worried about it all afternoon.