When I feel hard block coming, I do what they call 'easy onset'. Its basically taking a nice pause right before that word, breathing easy, and speaking as I exhale. Also, I used this technique in conversations with my friends, but for some reason I just could not bring myself to use the same technique when I was giving speech or speaking in meetings. Over time I realized that I was too afraid of how people would judge me. So I worked on not caring about what other people might be thinking about me. Now I use this technique pretty much anywhere.