I have done a lot of therapy (intensive, inpatient and weekly sessions) and I do actually have fair control over it now, but up and down for sure. It's not about having to get angry for fluency, it's the fact that it happens for some of us, and I have yet to hear a solid reason why. I think it's worth considering that their are many types and specific causes for dysfluency for us. I don't believe they're is any single prototype for stuttering or fluency.