I feel this is a really common narrative people use when they have lost hope in themselves and can't see themselves ever progressing toward being functional or independent. I've noticed people often use narratives like this to justify their inaction or protect themselves from blame or self-scrutiny, and after some time it becomes so deeply ingrained and automatic that the individual becomes stuck and unable to move on. If I had to guess, it comes from a place of deep insecurity and fear, that no matter what degree of self-improvement they make they will always be insufficient in the eyes of other people.