I have short fingers or as I like to call them 'PlaySkool' fingers. And thanks to having broken each and every one of them at least once, many more than that, I have to work constantly on dexterity and flexibility. But it gets better the more I play. My real problem seems to be a weakness in my left wrist. I have no idea how to build up endurance in the wrist. Is this a problem for anyone else? How do you correct that?