Self-delusion and self-loathing
Two shores of the same river, either can get you into a lot of trouble.
Self-delusion is lying to yourself about how good you are. You might think you're a world class designer or actor or chef or administrator or problem solver, but you might be merely well-intentioned, hard-working and pretty good. Which is fine, but pretty good is hardly remarkable. Telling yourself the truth about what you've got to market is the first step to marketing with success.
Self-loathing is lying to yourself about how bad you are. You might think you've got nothing to add, that you're a lame designer or actor or chef or administrator or problem solver, but you probably have the potential to be great. Awe-inspiringly great ...if you're willing to do the work, make the sacrifices and stop undercutting yourself. Supporting yourself with the truth about what you could market is the second step to marketing with success.