This is an interesting topic, thanks for posting.
Maybe I'm just terribly confused and deluded but I think my problem is the opposite most of the times but it's causing the same symptoms so to speak. I feel like I'm never good enough too but not because I want to be the best or better than others or anything. I've never been much competitive and I'm happy to give more than I take. Also if my doing doesn't affect anyone I don't really expect much from myself. Anything is good enough as long as I enjoyed the process of it. But I have this immense fear of letting people down or disappointing them. Not cause I worry about what they think of me but cause I don't want to be the cause for someone else's worries or problems. Which often makes life nearly impossible. I can feel guilt for eating the food that might have saved someone else's life in a poor country. I feel like a monster when I step on a bug and cause it's death cause I don't think my life is superior to any other life form. I can get so tangled up in these thoughts and I think it's cause I haven't developed much of an ego.