It's because we are extremely conscious while to people speaking. As per my experience, I think we all have those cliche Stutter words in our brain that when we try to speak, they come forward and we Stutter. It's hard to overcome them but I would suggest taking an appointment with the Speech Pathologist. Therapy will for real help you speak more fluently. However, it's not possible to overcome stuttering completely but if it's reduced, what else do we want?