I was reading this week in 2 Nephi chapter 4 - one of my favorite chapters. Nephi mourns the fact that he has weaknesses but then rejoices in the Lord. There are a couple thoughts that come to mind in pondering these verses.
First, if even Nephi, as great a prophet and example of strength that he is, gets discouraged, as in verse 19 where he says "My heart groaneth because of my sins", it gives hope to the rest of us, that even those we look up to face many of the same temptation and problems as we do.
Then later he turns around his attitude and says, "Rejoice, oh my heart, and give place to more for the enemy of my soul." I wonder, what was Nephi's "enemy of his soul." Was anger against his brothers? Then I think what is the enemy of our souls? It's different for each of us - it could be addictions, or inability to forgive, or laziness or pride or covetousness or any number of things. But whatever the enemy of our soul may be, we follow the counsel and example of Nephi to overcome it through calling on the Lord even as Nephi did in faith.
I love the final verses of that chapter:
Oh Lord, wilt though encircle me around in the arms of thy righteousness ... O Lord I have trusted in thee, and I will trust in thee forever ...Yea I know that God will give liberally him that asketh."