What does this quote mean - all other swindlers on earth are nothing to self swindlers?

This quote suggests that the worst kind of deception or manipulation comes from oneself rather than from external swindlers or con artists. It implies that being self-deceived or misguided in our thoughts, decisions or actions constitutes a more insidious and potentially damaging form of manipulation compared to being deceived by others. By emphasizing the significance of self-deception, the quote encourages individuals to be self-aware, critically examine their beliefs and behavior, and avoid self-destructive patterns of thought and action.