One of the reasons people stutter is they think they're going to but they aren't. So they pre form their tounge and get ready to prevent the stuttering but in doing so they make themselves stutter.  Normal speech isn't perfect. It has natural stutters or breaks. The stutter thinks that normal speech is perfect. So they try to be perfect. The stutterer also talks faster than a normal person. By slowing down and not thinking about what's coming next can help fluency.  All these things have significantly increase my fluency.