Conqueror

The exact timing of the first part of Section 10 of the Doctrine and Covenants is sketchy, but it was during the period of the translation of the Book of Mormon. Joseph Smith had loaned the first 119 manuscript pages of the translation to Martin Harris to show his wife and try to win her support. Martin subsequently

lost the manuscript. Joseph was inconsolable over the loss, not only because he had let the sacred writings out of his hands, but because the Lord had warned him twice not to let Martin have the pages. When it was evident that the one and only copy of the manuscript would not be recovered, Joseph inquired of the Lord what he should do. 

In response, Joseph received this revelation from God. The young prophet had an important lesson to learn about men and about Satan through this experience. A part of this heaven-sent lesson included this commandment about prayer:

Pray always, that you may come off conqueror; yea, that you may conquer Satan, and that you may escape the hands of the servants of Satan that do uphold his work.
--Doctrine and Covenants 10:5

Because Satan is unrelenting in his attacks upon us, we must we constant in our defenses. Prayer is the link that holds the whole armor of God together for us. 

When I fail to pray, for whatever reason, I give the devil an opening, an unprotected place where he can slip in a thin blade of temptation, a barb of jealousy, a dart of greed, an arrow of anger. Constant prayer cinches up my armor and closes any gaps. 

The devil hates to hear me pray because he knows I am prepared to meet him, and I am forcing him into a corner. He has no problem overcoming me alone with the natural man ever at work from the inside on my defenses. It is quite another thing, however, when he has to face me and the Lord. I cannot conquer Satan by myself, but with God's help—His enabling grace—we can together defeat the adversary and come off conqueror.