From THE SOURCE OF FAITH IS FAITH ITSELF by Rabbi Aharon Lichtenstein

At one point, during my late teens, I was troubled by certain ethical questions concerning [the destruction of] Amalek etc. I then recalled having recently read that Rabbi Chaim Brisker would awaken nightly to see if someone hadn't place a foundling at his doorstep. I knew that I slept quite soundly, and I concluded that if such a paragon of kindness coped with these laws, evidently the source of my anxiety did not lie in my greater sensitivity but in my weaker faith. And I set myself to enhancing it.

http://www.heritage.org.il/innernet/archives/faith.htm