How often do you hold your breath? Can you ever relax or are you always tense? Have you ever just sat in a chair and just sat there breathing without thinking of how you are breathing? Try observing some who is breathing when sleeping. It is a very normal and passive breathing. This is how a fluent speaker talks. When you have relaxed and continuous breathing while speaking so that your vocal cords are always open, you cannot stutter. This is how I basically became fluent without any relapses.