I think part of stuttering is all this extra overhead pertaining to our anticipation and perception of words. Many of us are easily able to discern another stutterer (however covert). We pay a lot of attention to details, and relate it directly to our own ability to communicate. It might not always be the case that our predictions are correct, regarding whether we would fail or not, but that's part of it: The insecurity, the suspicion, the precaution. And then we dodge and weave words the best we can.