I recently enjoyed listening to this interview with someone who knew Grothendieck. It takes a while to get going, but some of the stories are quite gripping.
“Look, I can take on anyone in Math.” — don’t forget, this guy [Serre] is the youngest Fields medal winner ever, the first Abel prize laureate, etc. — “I can understand the reasoning of the greats, handle them new ideas, you name it.”
“Except for Deligne.” (WHAT ?)
“Deligne is totally out of my league. Above my head.”
“The difference between Deligne and me, is the same difference between me and an average good mathematician.”
I found this anecdote especially astonishing considering that at the time I had never even heard of Deligne. (And most people, of course, haven’t even heard of Grothendieck.)
[1]: https://www.quora.com/What-is-the-height-of-confidence/answe...