good enough?

As friend of mine came to my room and poured out her feeling of agony about how she felt inferior to many things in her life, and how she felt overwhelmed by them. It just got me thinking, while I look at her as someone who does a lot of (interesting and adventerous) things, which I consider wow!, her reflection of herself was rather the opposite - she thinks she not good enough.

I did get me thinking how good enough is good enough? Who sets that standard of excellence? Do you say you are good enough when you pass or excel in your exam? And when you are good enough, is that barely good enough to scrap through one thing; or is it good enough to be barely excellent? Maybe barely isn't even sufficient to describe this phrase?

Some do think it is redundant to ask and think of such issue.