Technique! Just make sure you push and pull the chuck straight up and down. And you know it's a delicate thing. Don't strong-arm it when unscrewing and screwing the valve. If you're using a frame pump of a type that doesn't clamp down on the valve stem, get one that does. It's a lot easier. And also, when using a frame-type pump that doesn't have a hose on it, you do have to hold it onto the valve stem in a way that keeps the pump stable and straight by wrapping your fingers around it and the rim. If you are going far from home, take a spare tube. Sometimes you WILL break a valve, or you might get a flat that you can't easily patch.