i had a very severe stutter from when i was 11 til 16ish. there were a couple things that helped me. tl;dr eliminating secondary behaviors, practicing natural breathing patterns, not “slowing down” // first i realized that secondary characteristics (fast blinking, odd sounds, literally punching my leg to get a word out) were entirely voluntary and just conditioned habits basically. so i tried to notice when i would do those behaviors and eliminate them. my stutter got harder at first, but then it finally started to improve. once my stutter was more moderate, i tried to work on breathing patterns. i had gotten used to hammering through a word for 30 seconds and then gasping for air. but most fluent ppl breathe at the end of a sentence, or between phrases. so i tried to imitate more “normal” breathing patterns, til it became natural to me. also wanted to add that slowing down never helped me. trying to control the rate of my speech, whether it’s to slow down or speed up, made my stutter worse. so i don’t try to control my speaking rate. i still have a stutter, but it is mild. i tend to talk slower than average, but i don’t usually feel tense or frustrated unless someone is demanding that i talk faster.