Anxiety can and does effect you mentally . If your anxiety and doubt about yourself gets to such a level I'm sure it could block your expected arousal reactions . If it happens a few times I'm sure it would start becoming an elephant in the room where you start focusing on your anxiety instead of what is supposed to be a pleasurable experience .
But your question is if anyone has ever had a performance issue . Yes I remember having one . I was 17 and it was my first go at it . I had been waiting to get my license for months so I could go to the hookers 60 miles away . When I got there I was so nervous I couldn't get it up . Felt destroyed . Dragged my *** away and spent the next week in deep thought of what could be wrong with me . I went back in grim determination a week later and while not breaking any records I got the job done , and was away after that . So yes anxiety about anything can play a part .
Pretty much you've got what you've got as far as size goes . Don't let it ruin your intimacy with a partner . You can give yourself and your partner enough pleasure if you focus on that pleasure ..and not things you can't change .
Best to finish with a joke . My mate told me a good one years ago . " guy takes of his pants ...girl looks down and sez ..who are you going to satisfy with that ? .. guy sez " me , I'm going to satisfy me with that "