why do girls do the things they do?

This morning as I was getting dressed and ready to leave for work, I was looking through my drawer for things I could "accessorize" with. I decided since I didn't have a brown necklace like I really wanted, that I should add a headband. However, the headband I was thinking of gives me a MASSIVE headache. I thought for a second and decided I really shouldn't wear it because I knew (without a doubt) my head would be hurting about 5 minutes after I put it in. I thought for a few more seconds...and my conclusion?

I am currently suffering from a MASSIVE headache.

hence, my initial question: why do girls do the things they do?