When I've looked in the mirror through my life, I've judged my height or big I was through it. I think a lot of people do that.

I just realized though, that I'm twice as tall as I thought I was. That's why when standing next to someone else in the mirror, I think their size looks different... It's because when I see myself in the mirror, I'm seeing myself at twice the distance than I had really thought about.

I've realized this concept before, for example on many car mirrors it says "objects may be closer than they appear." This is because I'm seeing things from my distance to the mirror, then the mirrors distance back to me.