But some of God's children are not at that point yet. From His infinite mercy, Christ meets us where we are and then seeks to elevate us. Coming unto Christ doesn't necessarily happen in an instant. If fear of punishment is all we can understand, then Christ will motivate us based on fear. The scriptures say, "Fear God". Only as we are motivated (even by fear) and begin to obey, can we begin to come to know Christ more and then refine our motivations. One day every knee shall bow and tongue confess that Jesus is the Christ; many, I expect, will be motivated by a desire to avoid the eternal punishment. (Phil 2:10-11; Rom 14:11)
After fear, God entices us to serve Him by promising us unspeakable rewards. Heb 11:6 But without faith it is impossible to please him: for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him. Christ Himself commamded that all people "lay up in store treasure in heaven". Positive reinforcement is a higher and more enduring motivation. And as we serve and obey God, we come to know Him better, and His attributes. As we learn of Christ and serve Christ, our faith, and motivations are further refined.
John 15:10 If ye keep my commandments, ye shall abide in my love; even as I have kept my Father’s commandments, and abide in his love.
The highest motivation for devoting our lives to the service of Jesus Christ is out of pure love. If we come to truely know that perfect attributes of Christ and His infinite love and mercy for us, how could we not adore Him and serve Him. The Book of Mormon prophet, King Benjamin, reminds us that only by serving God and participating in His work can we truely come to know the Master.
Mosiah 5:13 For how knoweth a man the master whom he has not served, and who is a stranger unto him, and is far from the thoughts and intents of his heart?
Again, pure love (charity) for God, is the highest, noblest, and most enduring motivation. But we cannot begin to come to know Christ until we begin to learn to put off the natural man and act with restraint (Thou Shalt Not's). We then further progress in our knowledge and love of God by participating in Christ's Kingdom (Thou Shalt's).
John 14:15 If ye love me, keep my commandments.
In a way, our motivations may stratify us in heaven and in the resurrection. If we at least confess Christ, even out of fear, we are promised to be eventually saved from Eternal Punishment. Our motivations based on fear, reward, or love likely determine our level of faith and obedience which may also determine our place (mansion) in heaven. (see 1 Cor 15:40-41).