I just read this brilliant blog post by the Glasgow Dog Trainer (John McGuigan), which I thought I'd share. Even the top-notch guys can get frustrated and try to push on too hard. https://glasgowdogtrainer.wordpress.com/2017/06/27/logan-part-6-train-the-dog-in-front-of-you/
One of the gundog trainers advocates teaching the hold with treats for the dog and a bottle of wine for the trainer