Try this when you get a block. 1. Stop yourself. Do not try to grunt or force out the word, because that just reinforces the bad speaking habits. 2. Breathe. Not a deep breath to the back of the throat, but a normal breath that you can feel going just past your lips. 3. Rewind. Go back to the beginning of that phrase. 4. Link. Connect all the words in the phrase together as if it were one big word, and ride the wave. This strategy has been very effective for me since I started using it about a year ago.