Congratulations I beat it, too, in my mid-twenties. I had figured it out. My confidence, breathing, forming the word(s) in my mind before attempting to say them. Everything was in sync and the planets were aligned. I finally felt normal. That was until I had a midlife crisis, and it slowly came back. The code I had deciphered began to encrypt itself again and I haven't been able to fully crack it since. It's all mental. For me, it's primarily driven by stress these days. The more stressed I am the more I stutter.