Sometimes, I'll anticipate trouble and rephrase. Sometimes I can manage if I hesitate slightly before continuing. Other times, I'll just power through it, in stubborn spite of block/repetition, if I really want those particular words coming out. Most of the time, I prefer the latter solution. But in some periods, it's convenient to be able to regulate my stress levels by deferring to the former ones. Not that they guarantee fluency, of course.