On the whole I agree, people who desire to be good at something usually know when they're not good. While they're working on their skill and sharpening their mental tools, they are likely to get frustrated and quit. Ira is saying, don't quit, understand that this 'dark stage' is the process, and work through it.
Summary?
The essence of this 5:20 video is to say that creative artists should be patient with themselves during that phase of their creative life when their taste exceeds ability to create:
So they cannot then create something that meets their own standards.
Amazingly, 395 reviewers of the youtube video gave it an average of 5 stars. Whatever.
Ira is a great story teller. But this is not a story: it's a blog post. [This picture is worth less than a 1000-word summary. (or 100 word summary) ]
Maybe the other parts (#1 & #2) are more worth.
Who said it was a story?
This is a 4-part interview with Ira Glass on storytelling. I thought it was pretty insightful.