Yes, I am only 23. I got my first job out of university, and basically my stammer ruined it for me and I quit after 6months. One important thing I learned, is do not try to avoid speaking. I got into a habit of writing everything, so if I got stuck on a word my co-workers would just say "you can write it if u want", this is annoying when you're trying to improve. So my tip would be embrace your stammer, don't let it control you just keep trying and eventually you will hopefully get into a groove and it wont be so bad. The worst thing you can do (which I did) is try to avoid talking and avoid asking questions because that just makes things far worse in the long run compared to the maybe few minutes of stammering otherwise. ​ ​