So, brilliant me that I am, I'm sharing a few of my observations. And, since I would never wish to malign the revered Mr. Jordan who is not only published and very popular but, well, dead, I'll use examples from my own writing to illustrate the point. I have to say here that I greatly admire Robert Jordan. He died with his boots on, as it were, a worthy goal to strive for.
Lesson #1: Beware Character Creep
Writing for me is creating a world. It starts out a tiny microcosm as first one and then another character is developed, as they interact with each other and as I, as a writer, get to know them. (I don't develop characters so much as grow acquainted with who they are). Then, as they move through the plot, they interact with more characters who in turn start to reveal their personalities, and with them their back stories, in an ever-expanding spiral.