Dopamine is related to your need. When you are in love, and it's working, you stutter less, because you don't want to be fluent but to get the girl/boy, and these are not the same "excercises", so if you want love more than speaking (and it works) than you don't stutter (that much).
That's true for all the activities. Have you seen the almost unwatchable video of the severe stutterer who volunteers to a play, and actually he manages to say his lines fluently (it's on youtube)? And after that he falls back to severe stuttering. That was because he was under pressure to act, so he miracoulosly "forgot" about stuttering for that highly dopamine-flooded moment. Because his dopamine was not related to stuttering.
(That's why from Demosthenes to Churchill and Bruce Willis so many stutterer chose an orathorical career. They are the compulsive masturbators who are recovered by being prostitutes. Sorry about that metaphor, but that's very accurate.)
Fluency-obsession is the strangest elixir, because if you drink it, you stutter. And even if we now that, we must drink it. I wonder, why.