For me, it was working. Getting a job after high school and being forced to talk gradually got me out of it. I remember taking almost half an hour to tell an ice breaker in elementary school (not kidding, the teacher felt so bad she just let me sit down without saying it) and struggling to read out loud in high school, and being scared to take the drive thru mic for Starbucks, but after a couple months a lot of people would tell me my stutter was just gone. I hadn't even noticed. My biggest motivation to work through it was the King's Speech. I know it's psychological and not physical. I had a speech therapist whose bullshit I could smell. Something about her plaques seemed phony. She had me read a book and I breezed through it without a single stutter and the best part was when she said in frustration "could you pretend to stutter so we can work on it". Mind you, I still stuttered at school and at home, but that's something I'll never forget. I think it has to do with who you're comfortable talking to. Working made me comfortable talking to random people. I still stutter when I'm talking out the side of my neck but it's kind of worked itself into my speech pattern. For example, if I'm saying the word Fuck, I'll sometimes have that slow pause on the F, so it sounds like Fffffffffuck. But if anything, the Fuck has more power and enthusiasm. But yeah, these are just my experiences with it.