I Remember doing a job interview, it was a group interview and there was another candidate next to me. Stammered a couple words and interviewer was like... "Thank you for your time" Thrn the interviewer focused entirely on the other candidate. Barely acknowledged me when it was over. I've also been laughed out of presentations. I watched a couple bill Clinton speeches, practiced his speech patterns, pauses, and now in both of those cases I sound pretty damn presidential lol. I'm not a bad stammerer. It's mild to mostly non existent. I'm good with word substitution, and calming myself down before I speak. But that hurt. I'll never forget that. I know one other colleague that does stammer badly, and I always listen to her patiently. I don't pull out my phone or distractedly look elsewhere. I don't know you, my advice is to get into an industry where communication is important. Get into toastmasters. Force yourself to communicate, talk to yourself if you have to. Its going to suck, but it's the only way I got better.