Read an interesting tip in Self:

"Forming an O with your mouth makes putting on mascara a cinch, says Allyson Murray, a makeup artist in NYC for Jane Iredale. When you hold your mouth like this, you relax your eyes and blink less." (pg. 66, June issue)

Makes sense to me. Are you sitting at your computer with your mouth in the shape of an "O" testing it out? Because I totally did that too.