The first time I saw this idea was in the commentary of the Gra on Mishlei on the verse זבחי שלמים עלי היום שילמתי נדרי "Today I sacrificed peace offerings. I fulfilled my vows." That is: the evil inclination starts out asking one to do a good deed.
The exact details however are not clear to me--that is how to go about evaluating the situation. As a general rule, I think the best idea is that of Rav Israel Salanter--to learn the basic set of Musar books to get a clear idea of what the Torah actually requires of one--in a practical day to day sense.