A thesis advisor in regard to working on one's thesis: "The yetzer hara is particularly strong during thesis work."

"The yetzer tov is good, but the yetzer hara is very good, because without it a man wouldn't marry, procreate or go into business." (Talmud Ber 61b)

"He was going to give up smoking—but his yetser ha-ra got the better of him." (Glinert)