Chief and I are trying to learn a little about basic handling. He does pretty good on force to pile. I have a hard time getting him to sit on a retrieve (his basic obedience is excellent). The only time he will sit on a retrieve is with collar pressure or check cord pressure. After I apply even the lightest pressure he becomes very timid. He runs with his head down and heals directly behind me. He continues to do this until we both become frustrated and the training session ends. I have never been heavy handed with him, but he was CC when I got him. Where do we go from here? Is it because we spent our first couple of months together getting used to each other with no collar?