To be a successful missionary one must have the Spirit of the Lord. We are also taught that the Spirit will not dwell in unclean tabernacles. Therefore, one of the first things a missionary must do to gain spirituality is to make sure his own personal life is in order.
Ezra Taft BensonWhat does the Atonement have to do with missionary work? Any time we experience the blessings of the Atonement in our lives, we cannot help but have a concern for the welfare of others. ... A great indicator of one's personal conversion is the desire to share the gospel with others.
Ezra Taft BensonA woman whose life is involved in the righteous rearing of her children has a better chance of keeping up her spirits than the woman whose total concern is centered in her own personal problems.
Ezra Taft BensonYou must not allow yourselves to become discouraged. Missionary work brings joy, optimism, and happiness. Don't give Satan an opportunity to discourage you. Here again, work is the answer. The Lord has given us a key by which we can overcome discouragement: "Come unto me, all ye that labor and are heavy laden, and I will give you rest. Take my yoke upon you, and learn of me; for I am meek and lowly in heart; and ye shall find rest unto your souls. For my yoke is easy and my burden is light."
Ezra Taft Benson