Honest answer I think you just care less and less what others think, which is fundamentally what stresses us out as stammerers making it worse. I still have ups and downs but manage things far better, I know what makes it worse and what helps, but there’s no magical fix. Outside of the stammer my life is great - 95% + of people don’t care about your stammer, so relationship wise if someone does it’s a great way to discount that 5%, but my fiancé couldn’t give two hoots about it when I do stammer. It’s not an overnight change and comes with time - I honestly think with age in life you become more inclined to not care about others views (even outside of stammering) which in turn makes things so much better. 20s and teens are tough for everyone, stammer or not!