Staying Up Late at Night

Rav Chaim was asked by a Rosh Yeshiva the following question:

I often tell my talmidim to get an early start in the mornings and not to stay up late.  They respond that there are many stories of Gedolim who stayed up late at night to learn.  What should I tell them?

Rav Chaim zatzal answered: “One cannot bring proofs from stories as their circumstances were different – they only did so at that point in their lives if they knew that it would not affect them.  One must know that even if there is no immediate effect, it could affect them negatively later on.. I personally would go to sleep in the afternoons whenever I felt tired even for a few hours, and that was why I was able to learn late into the night. (Kol Mishaalosecha p. 200)