eternal mysteries of life

I have proposed this question to many people, yet have not been able to ascertain an answer.

Why don’t people work from the top down when they are taking a shower? When I take a shower, I wash my hair last. You would think that this doesn’t make sense; You are washing all the nastiness out of your hair and when you wash out your hair, it just runs down your “clean” body. I mean, I am no clean-freak or anything, but this simply doesn’t make sense. And other people have told me that they follow the same pattern.

I mean, I am not going to change and start washing my hair first, but it is something that has left me in mystery for quite some time.