Yes I have experienced this too. I'm 90 - 99% fluent in situations where I feel confident both in myself and in my speech (I used to range between 30% - 70%). These moments of extreme speech confidence used to be scarce and usually did not last very long. Therefore one way to reach a self cure is to increase the lenght and quantity of these moments of confidence. Lack of confidence is caused by a negative internal belief. Internal beliefs can be changed if your willing to work for it. Also confidence and fluency work like a snowball rolling of a giant snowy mountain. The more positive experience you have relating to your speech and self image the more confident you will start feeling which will result in even more positive experiences. This works in both directions, the more negative experiences that you have the more your confidence meter falls. To gain speech and self confidence the amount of positive experiences you have need to outweigh the negative ones. I could go on about this for an hour but I'd rather recommend you this book which goes in on it much more extensively. " Stuttering & Anxiety Self-Cures: What 100+ PWS Taught Me " by Lee G Lovett