Self narratives are the stories that we tell ourselves, about ourselves. Delusional self narratives are stories that we tell ourselves, about ourselves, that might not be totally grounded in reality.
The delusion that I tell myself is that because I am a high achiever, I can achieve my goals. In reality, I cannot. Not because I'm not a high achiever (anyone who has met me would agree that I am), but because nobody can achieve difficult goals. They can only achieve a difficult goal. One at a time.