The pace of overcoming social anxiety is never predictable. Sometimes setbacks will occur but when they do, it is important to realize that if you get up and keep going all the rational therapy is still there. Sometimes you can go through longer periods where nothing works as it should. Keep your rational reminders and rational therapy going even when it's difficult. Your brain has to change and sometimes changes occur when we are feeling like nothing is working. If you stick to your rationality and keep reinforcing what is rational you come out on top in the end.
No one who has learned to be rational and has applied these methods in regular life situations ever loses any of this rationality. Leftover automatic negative thoughts (ANTs) may be playing a mind game with you. However, if you've been faithful to the therapy, you have nothing to fear. You are going to be more than okay. Remember, you can't have a setback unless you have already made some progress!