Alma 13:3-6 provides us with lots of information about our pre-mortal life and about the consequences of our choices in this life.
In Alma 13:3 we read that priests were "called and prepared from the foundation of the world."
Why is knowing this doctrine … that we lived in the pre-existence with God and perhaps called and prepared to do things on this earth … important?
If we believe that we did not exist before this life and that there is no life after death, then our actions might be significantly different. Knowing that we were called and prepared before this life, we will seek out what our mission in life really is … that we have a purpose that none other can do. In contrast, if we do not believe in a pre and post-mortal life, then what we do in this life would really not matter. Indeed we could eat, drink and be merry.
Satan knows well the implication of our knowing about a pre and post-mortal life. If he can get us to think that there is nothing more before or after this life, then he can more easily convince us to sin.
Elder Maxwell said, "Meanwhile, the adversary relentlessly uses the absence or disbelief of this doctrine to shrink man’s perspective. One-dimensional man with only a one-dimensional view of the world will surely focus upon the cares of the world, yielding to the things of the moment."
He continues, "Premortality is not a relaxing doctrine. For each of us, there are choices to be made, incessant and difficult chores to be done, ironies and adversities to be experienced, time to be well spent, talents and gifts to be well employed. Just because we were chosen “there and then,” surely does not mean we can be indifferent “here and now.” Whether foreordination for men, or foredesignation for women, those called and prepared must also prove “chosen, and faithful.” (See Rev. 17:14; D&C 121:34–36.)" (Neal A. Maxwell, “Premortality, a Glorious Reality,” Ensign, Nov 1985, 15)
This last part echoes Alma's teaching when he said that these priests were "left to choose good or evil." So even though we are called and prepared to fulfill missions on this earth, we still must exercise faith and choose correctly to inherit the blessings our Father in Heaven has prepared for us.
Abhorrence of Sin
Possessing an abhorrence of sin (Alma 13:12) stems from living a pure life. As we keep the commandments and purify ourselves, our desires and motivations become more and more aligned with the desires and motivations of our Heavenly Father.
As with anything in life, we can develop an aversion or taste for various activities. Just as a small example, I offer something that has happened in my life that is applicable. For most of my working career, I've commuted to work every day. On my commute, I would usually listen to talk radio or music. Some of the things I used to listen to would drive away the Spirit. I recognized this and decided to begin listening to either more uplifting music or the General Conference talks. After several days of listening to the General Conference talks, I temporarily switched back to listening to the radio. Some of the things I heard on the radio offended my spirit and I could hardly bear to listen. I quickly switched back to the General Conference talks.
Choosing the right and daily sanctification is much like a fire. At first it may be small, but as you throw more fuel onto the fire, the fire grows and it becomes difficult to quelch.
Wresting the Scriptures
In Alma 13:20, Alma warns against wresting the scriptures. To wrest means to violently twist or turn or distort. We need to be careful in how we use scripture.
Alma concludes his remarks with wise counsel.
Don't procrastinate your repentance
Humble yourself before the Lord
Watch and pray continually
Be led by the Holy Spirit
Be meek, submissive, patient and full of love and long-suffering
Have faith on the Lord
Hope for eternal life
Have the love of God in your hearts always.