I did a year or two of speech pathology in elementary school, but I question its effect considering my stutter lasted quite a few more years beyond that until it mysteriously vanished. I did some casual meditation in those later years, but nothing I would refer to as CBT (my wife is a professional children's mental health therapist and has mentioned this as well). The only thing I can sort of draw a parallel to is that I did begin to learn that breathing (and rhythm in general) had a lot to do with how an oncoming block or stutter was going to affect me. Deep breaths before speaking probably had a 50% success rate and getting me through a hard consonant block. Tapping my hand on my thigh in a particular rhythm and cadence matching my speech sometimes seemed to help avoid a stutter altogether as well. Not always, but often. My go to response was actually simply finding other words to substitute as often as I could. And there didn't seem to be any rules there - even if a new substituted word was mechanically similar in structure and sound as the word that was giving me trouble, for some reason the new word (or phrase) I would come up with would simply come out unaffected. As if, if my brain didn't have time to dwell and focus on the problem, it would simply move along and spit out whatever I was coming up with to fix the problem. I would say my confidence managed to improve as I progressed through high school and young adulthood (to the point I went into sales, haha). Between 19-25 years old, I definitely came out of my shell socially and this also seems to be approximately the time that my stutter stopped showing up (noticeably or frequently).