I improved my stuttering a lot. During my junor school life especially when I was 15 y.o my stuttering deteriorated to the peak and even when I practiced pronouncing certain sentences myself without materials(aka so-called 'practicing pronounciations') I would at times stutter as well, I tried intiminating normal speakers' speaking to mitigate/cure stuttering, reading materials, and practicing tongue twisters but still my stuttering was bothering me after I tried all of them. Gradully I gave up fighting against my stuttering but to my surprise when I was 16.5 y.o my stuttering nearly went away! And I cannot imagine how smooth my speeches had become during that time even myself and for once I thought stuttering is a purely psychological disorder but O.C that is not the fact and just my wrong self-conjecture. So to recap I DID NOTHING to improve my stuttering a lot and just let it go then my stutteing was improved a lot spontaneously so in my case mindset is the very main factor playing role in mitigating my stuttering.