And truth is knowledge of things as they are, and as they were, and as they are to come...
Doctrine and Covenants 93:24
The real reward for pain is this: self knowledge. - Lance Armstrong
I think it is one of the hardest lessons to learn - that who we are is reflected by how we act; "Wherefore, by their fruits ye shall know them" (Matt. 16:20). Our character is not something that can be taken off and put back on, nor does our accountability sleep. We are accountable for all of our actions, past the age of accountability, and it seems that much of who we are is the accumulation of our choices.
Who we are, then, is very important. Do we like who we are? Let me be honest: Do I like who I am?
I hope that I can consistently answer "Yes." But there are times when I cannot, and I believe that in these times the Atonement must be sought. Faith is a principle of action and power (True to the Faith), part of which includes a supreme, consistent effort to get better.
As faith is exercised over time through work, prayer, study, pondering, and worship, we - I - can be given the assurance that "I can do all things through Christ which strengthenth me" (Phillipians 4:13), even change.
Joseph Smith put it beautifully: "Therefore, dearly beloved brethren, let us cheerfully do all things that lie in our power; and then may we stand still, with the utmost assurance, to see the salvation of God, and for his arm to be revealed" (Doctrine and Covenants 123:17).
This doesn't apply only to sin; I believe that it is through the Atonement of Christ that we become the type of person that we ultimately want to become. Here in mortality, that includes the major attributes of charity, humility, mercy, faith, hope, etc. over long periods, and also can help in the immediate: how will I behave tonight? Will my behavior this hour help me become more like Jesus Christ?
I think this leads up a path of ever-increasing consecration to God and His work. This is not to say that we do not pursue supposedly temporal interests; rather, our perspective on temporal things becomes more like God's:
"Wherefore, verily I say unto you that all things unto me are spiritual, and not at any time have I given unto you a law which was temporal; neither any man, nor the children of men; neither Adam, your father, whom I created" (Doctrine and Covenants 29:34)
We start to see our lives like the Lord sees them - times of rich and eternal opportunity. That, in turn, gives us greater motivation to become what we can and must become: children of our Heavenly Father; men and women of God; men and women of sound understanding, who hunger and thirst after righteousness; the Zion of our God.
Simply, this: Though I make mistakes, I know that God is faithful, and that through my Savior Jesus Christ, I can become like my Heavenly Father and dwell with Him again.