Dog Training - If a Dog Freezes in Fear, How Do You End on a Positive?

If a dog freezes in fear, how do you end on a positive versus ending when they're still shut down? I don't even believe in that philosophy. And i notoriously go too far with this kind of training because my dogs tolerate it beause they have years of experience working with me. So if we've been working for a long time, it's time to wrap up.