Some people say not to move the head when playing tennis but to keep it very still. I agree with this. But when volleying you are supposed to bend the knees to get down for low volleys but now the ball is moving along with the head. Since I have back problems sometimes probably from being tall, I have the lazy habit of not bending the knees and just moving the racquet to the ball while keeping my head still and it sort of works but the better volleyers I have see all bend and get down for those low vollies. How does one break themselves of this bad habit of not bending since sometimes bending can cause back pains. Do I just need someone to drill with me and yell at me everytime I don't bend the knees and instead keep my head still until I get into ingrained into my head to bend instead?