When one is struggling with mathematics, it is sometimes nice to know that even winners of the Chern medal, sometimes have difficulty following mathematics. From this beautiful interview of Nirenberg,


comes this gem from Peter Lax:

When Peter Lax and I were students, he always knew more mathematics than I did and that continued thru-ought our lives. And very often he would explain something to me and sometimes I would forget and ask him to repeat and once he said, ” You know, I am happy to explain things to you several times, not more than 10 times. “