I just thought one clarification is needed so my issues with bad object lessons are not misunderstood. While I believe it is wrong to teach that we shouldn't sin implying in any way that we can never be fully clean, I do agree that we should keep the commandments and not sin. The problem is--we don't. (1 John 1:8). Thank heavens for the Atonement and the opportunity to repent!
But here are my reasons why it is better not to sin in the first place:
1. Because we already promised to keep the commandments at baptism and renew that promise every week in the sacrament. In fact, one of the things we need to repent of when we do sin is breaking this promise.
2. Because we love Jesus.
3. Because when we sin, we crucify Him afresh. This makes sense when you consider that the Atonement is infinite and eternal. When Christ suffered, He suffered for me at this time. And when I sin, I cause that suffering that He suffered then. (D&C 19:13-20).
4. Because when we sin, the Holy Ghost cannot abide with us and we are unworthy to enter God's presence (Alma 11:37; D&C 20:77, 79; Moses 6:57). We can become "past feeling" so that we cannot even hear the Holy Spirit which is exactly what we need to accomplish repentance and return to the presence of God. Who wants to take that risk?
5. Because when we sin, there are often consequences that are not easily repaired. There are scars, open wounds, even death and life that must be dealt with. And there could be serious wrongs creating emotional, spiritual, physical illness that cannot be resolved in this world. The scripture references for this are the constant reminder that the sins of the fathers [and mothers] can be visited upon the heads of the children. (Exodus 34:7; Lamentations 5:7). It's not the children's fault, but they suffer the consequences of the sins of past generations. The Atonement covers these pains and sorrows, but some will not be healed until we are in a better world. (Isaiah 25:8; Revelation 7:17; 21:4). I believe this is the great work in which we are now engaged that will continue into the Millennial Reign as we turn the hearts of the fathers to the children, and the children to their fathers (Malachi 4:6; Joseph Smith - History 1:39). And heal.There may be no object lesson or even parable fully adequate to address the powerful blessings of the Atonement and our responsibility to keep the commandments. (We sometimes do need to be a little more clear as to what they actually are, but deal with your bishop and the Lord as you see fit. And stop judging others unless you have keys to do so).
Bottom line, as John the Beloved said:
My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:
And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.
And hereby we do know that we know him, if we keep his commandments.