This is good writing advice. Sometimes in writing we get so wrapped up making our characters strong, brave and perfect. And we forget that she is afraid of spiders, and he is terrified of disappointing his parents. We have flaws and it is in these flaws we find truth, as writers and readers. She finds the courage to catch and remove the spider and he tells his parents he isn’t an all star.
The term Mary Sue came up a few months ago and I had to look it up. A “mary sue” is a perfect character that always sails through her/his story without a hiccup. They solve every problem their writer throws at them like its nothing. I have serveral “mary sues” and I am trying to fix them.