From my own experiences its almost always directly based on how much attention I am putting on stuttering. The more I think about it, the more I stutter. I try now to focus on it as little as I can which is a work in progress to re-train my mind to work normally but it certainly does help. Some days however when my anxiety is high and I just can't control my thoughts it terrible. All in all I just try to stay positive and work slowly every day to improve myself