The blocking happens because you're afraid of stuttering freely. Afraid of audibly stuttering. As in, "h-h-h-h-h-h-i." And this resistance to causes you to go in a sort of panic response, which is the freeze part, causing you to block. I blocked all day. Then I decided to allow myself to stutter freely in the company of my wife at first. Before this, I always resisted stuttering freely. I never wanted anybody to hear me repeat. I absolutely hated that idea. I decided to give it a try and no more blocking. Stuttering, yes. But no more blocking. IMHO, it's really just a response due to resistance of your stutter. It does take a bit of courage to stutter freely in the company of another. My ego often got in the way. I felt awkward doing so with my wife at first, but it brought me many great insights about my speech. Would 100% recommend. You'll be amazed where you end up.