I wonder why bejewelled causes our fingers to hurt

I am so addicted to Angry Birds. My husband would ask when he calls: "are you killing those angry birds again???". Have you experienced that when you fail to hit the target, unconsciously you tilt the kindle or the ipad hoping that it willl help breaks down the targets? I do that unknowingly when I am so much into it. I hate when I fail to hit them and they seem to "smirk" at you.