>*"Why can’t I say a sentence but can say “never mind” without any issue?"* It could be because you paid closer attention to speech blocks when saying 'never mind' resulting in negative experiences. Because of this perhaps you lost faith in your speaking ability when saying 'never mind' and likely you then developed a belief to perceive stuttering (when saying 'never mind') as a problem and to be avoided. In a way to cope with this or try to fix it, it could have led to prioritizing unhelpful corrections (e.g, trying to time your breath with articulation which becomes harder during a fight, flight and freeze response resulting in perceiving a speech errors, canceling the speech plan or holding back speech and then a speech block occurs) (instead of putting complete faith in the forward flow of speech and spontaneous natural speech without paying attention to speech errors).