I bet when you're feeling confident or needing to say something out of some deep push, that overrides the fear of fumbling words. The flow of conversation and temporary passion keeps the irrelevant thoughts at bay. Some people simply have that sort of relatable vibe. You know some people ask and just seem so stern and impatient waiting for a reply while others kind of lay back and implicitly state the most important thing is the present conversation no matter how long it takes and what happens.