It is debilitating when that happens. As hard as it is, and the desire to power through a word...you have to stop. Just flat out stop. Don't talk. Don't say a word. Instead, take a deep breath. Then apologize, even though you don't need to apologize for anything, and say I am a stutterer, and today has been rough. Then try it again. Sometimes you will get a person who will wait you out. Other times, you get the impatient person who wants to finish your thoughts (Whom I want to eviscerate. Do not speak for me!). Or that rare jerk who says something stupid to you. I have found that we now live in a day and age where most people will be accommodating, especially if they know what you are struggling to do. You are still going to stutter, but if people know what they are witnessing, it takes the edge off.