My stutter has lessened the older I got and it is much better now I'm in my twenties. Confidence and maintaining a moderately good lifestyle helped me. It takes work but I pushed myself out of my comfort zone by speaking more, going to events and travelling. Staying hydrated, exercising regularly and a positive mental attitude helps in my opinion, like with most things really. I can only give advice from my what I think works and I definitely have bad days now and then, and I do still stutter but I'm more fluent now than I ever was. Your stutter might not ever go, or it might lessen as you get older but you can always help yourself to make it that bit easier. Hope this helps!