In creative endeavors human beings mix up their own dreams of success with the feeble output of their minds and arms. This is why my aphorism is "No authoer should comment on her own work" (although I do leave an opening for Jorge Luis Borges). There needs a little distance between the creative work and the evaluation.
Since most of what we do is shoddy, sloppy, poorly focused on incorrect goals, and left woefully incomplete one might first think this proclivity to mischaracterize what we do as simply a means to defend ourselves from just criticism. Not so. We also mischaracterize our good and successful work as poor and unworthy. To listen to us humans you would suppose we have set as our species goal the pursuit of the near to mediocre always erring to the false and ugly side of things.
Often I wonder why we humans can't just see and accept competence those few times we achieve it. Experience shows that we more typically see and claim mastery at moments of incompetence. My best guess is that we are supposed to work together.
My hypothesis is consistent with the fact that nothing is written or recited or carved or taught or sung or remarked or even observed unless it is based on the works of others which were read and heard and seen and learned and harmonized and noted and shared in the past.
In actual reality we have to work together. We have no choice. So what use to us would there be for the ability to identify success in that work we do while we are alone?