Gratefulness fights off Satan

I read a story the other day about a man who found the barn where Satan kept his seeds of discouragement and doubt.  He then overheard the adversary state to one of his followers that the only times his seeds did not reap discouragement and doubt, were the people who lived their lives in continual gratitude.

2 Nephi 9:52 - "Behold...remember the words of your God; pray unto him continually by day and give thanks unto his holy name by night.  Let your hearts rejoice."