I know where you're coming from. I have a slightly different perspective. I find my stammer is one measure of how able I am to express my true authentic self. I used to have a severe stranger and was very repressed and depressed. Whenever I worked on some part of my mental health and got to know myself better, I was more able to express my newfound self, i.e. more comfortable interacting with people and more fluent. Self-knowledge led to more free self-expression. If I'm speaking while incongruent with my authentic self, I'm more likely to stammer, so when that happens it's a pointer to examine where the incongruency is coming from, why I'm being inauthentic. Resolve that, I feel true I myself, and the problem goes away. I still think there's a neurological component, but I also think there's a psychological aspect which feeds into the neurology, and while the neurological condition might not be treatable, the psychological issues are. If we recognise what we can and can't change, then we have something to work with to make improvements.