When I was a bochur in yeshivah I had a scary experience. I had the zekhus of assisting a gadol ba-Torah in his last days. When R. Dovid Lifshitz got very sick, I was assigned the task of helping him out during davening. At the end of his life, I saw something incredible. He would come to the beis medrash and someone else would put tefillin on him. Then he would sit with a siddur and daven. I was waiting to see when he finished the page to turn it for him and I realized that he would keep davening the same page over and over if I let him. Sadly, the illness and the medication took away his memory and almost his ability to function. But one thing he knew, something that was in his very bones, was that he wanted to daven. When you strip away all of the learning, all of the accomplishments, what you end up with is a simple, kosher Jew. Deep down, that is what a gadol ba-Torah is – a kosher Jew.
"If I were to wake you up at 2 o'clock in the morning," R' YB Soloveitchik would often ask his students to get their instinctive responses, "how would you answer?"