Technique is vital as Devolution said. Make sure that you are using your leverage to your benefit as much as possible. I typically if they are real tight end up using the palm of my pushing on the bead up and over while grabbing and pulled the other side with my fingers (that wasn't a very good description). It's really the only way, and sometimes gloves help cause it can give you wicked blisters (or rather just rip your skin off).