I also believe that it is psychological. Example: I stand alone in my office in front of the mirror, speak a sentence with 20 words. The sentence comes out completely fluently. If I leave my office and want to say exactly this sentence to a coworker, nothing comes out except "um" and a stutter block.... There is something behind this phenomenon... we can speak normally :D I can't accept it :( , and the market economy doesn't take my stuttering into account either. I have to deliver results and be able to sell