The Effects of Sin
When man sins, something is lost, for mortal man, it is lost for at least the duration of the mortal existence. This does not presuppose repentance. Repentance is real, but it does not remove from us the effects of our actions, our habits. What is lost? What is lost is the purity we brought to mortality, and it is the function of the atonement, at a later time it seems, to purge from us these evil "effects". What is lost is a human being who is changed by the sin, who is no longer able to say to himself and God, "I have never sinned that sin," who will not be able, at least in this life, to forget the fact that he did commit sin. What is lost is a man who, having committed adultery for example, though fully repentant and forgiven, will be more tempted to do it again than had he never committed the sin at all; thus the struggle now becomes more difficult. It is like a man climbing a mountain, who, allowing Satan to get one of his hooks into his back with an added weight, will still be able to climb the mountain, but only with increased effort.
In a way, this is not all bad. The increased effort will eventually make us stronger, and hopefully more faithful, but the nagging presence of the sin is ever there. And ultimately, it is the presence of that "added baggage" that will allow us to welcome Christ into our lives to relieve us of that "excess baggage". We will willingly and gladly submit to Him. We will plead for his help, his deliverance from this great weight. Thus we also begin to see the difficulty of enduring to the end. Without sin, enduring to the end is most likely, with many sins, it becomes increasingly difficult.
Ships who ply the seas of the earth collect barnacles to their hulls. These barnacles increase the ship's drag and slow the ship down. Eventually they must be removed, the ship cannot remove them by itself, and they cannot be removed while the ship is in the water, sailing the oceans. But with the help of a "savior", the barnacles are removed, the ship is freed from the unnecessary drag, now free to travel at an increased pace through the water.
Thus we see the prevailing counsel to avoid sin, that it is better to not sin, than to sin and then repent. There is an earthly price we pay for succumbing to sin, that price is "the effects of sin." One's progress is hindered, slowed down, even damned. Thus, by sin, we squander the wonderful opportunity to progress rapidly in motality with the aid of a body.
This doctrine does not say that one cannot be forgiven, what it says is that when we sin, we are changed by it, and that change will remain with us during mortality. Consider the following explanations of this doctrine by church leaders past and present.
"Even after the sins of the past are forgiven, the one so pardoned will doubtless feel the force of sinful habits bearing heavily upon him. He who has been guilty of habitual untruthfulness, will at times find himself inclined, perhaps, to yield to that habit. He who has stolen may be sorely tempted, when opportunity arises, to steal again. While he who has indulged in licentious practices may again find himself disposed to give way to the seductive influence of the siren. So with drunkenness, malice, envy, covetousness, hatred, anger, and in short all the evil dispositions. There is an absolute necessity for some additional sanctifying grace...to root out from the heart concupiscence--the blind tendency or inclination to evil. The heart must be purified, every passion, every propensity made submissive to the will of God. Man's natural powers are unequal to this task." B. H. Roberts JD 16:319
"Some suppose that they can in the flesh be sanctified body and spirit and become so pure that they will never again feel the effects of the power of the adversary of truth. Were it possible for a person to attain this degree of perfection in the flesh, he could not die neither remain in the world where sin predominates...I think we shall more or less feel the effects of sin so long as we live." Brigham Young, JD 10:173
"The infidel will impart infidelity to his children if he can. The whoremonger will not raise a pure, righteous posterity...which will continue upon his children and descend to his children's children to the third and fourth generation. It is perfectly natural that the children should inherit from their fathers,...Not in accordance with God's wishes, for his wish is that men will not sin and therefore will not transmit the consequences of their sin to their children, but that they will keep his commandments, and be free from sin and from entailing the effects of sin upon their offspring; but inasmuch as men will not hearken unto the Lord, but will become a law unto themselves, and will commit sin, they will justly reap the consequences of their own iniquity, and will naturally impart its fruits to their children to the third and fourth generation.
Therefore to be justified is to be free from sin, to be legally right before God. To be sanctified is to be free from the effects of sin, to have had sinfulness and the enticements of sin rooted out of our hearts and desires. To be sanctified in regard to vice is to shudder and shake at its appearance, to feel a revulsion for whatever allurements would detour or detain the human heart." Robert millet, By Grace Are We Saved, pp. 54-55
The term repentance is used in the scriptures with several different meanings, but, as representing the duty required of all who would obtain forgiveness for transgression it indicates a godly sorrow for sin, producing a reformation of life, and embodies (1) a conviction of guilt; (2) a desire to be relieved from the hurtful effects of sin; and (3) an earnest determination to forsake sin and to accomplish good. Elder James E. Talmadge, Articles of Faith, Ch 5
The offer of the firstborn Son to establish through His own ministry among men the gospel of salvation, and to sacrifice Himself, through labor, humiliation and suffering even unto death, was accepted and made the foreordained plan of man's redemption from death, of his eventual salvation from the effects of sin, and of his possible exaltation through righteous achievement. Elder James E. Talmadge, Jesus The Christ, Ch 3
I do not know any other way for the Latter-day Saints than for every breath to be virtually a prayer for God to guide and direct his people...if you are talking in the house, visiting in the social party, going forth in the dance, every breath should virtually be a prayer that God will preserve us from sin and from the effects of sin. President Brigham Young, Discourses of Brigham Young, Pg 43