Moroni's words really speak to me. Verse 25 of Chapter 9.
25 My son, be faithful in Christ; and may not the things which I have written grieve thee, to weigh thee down unto death; but may Christ lift thee up, and may his sufferings and death, and the showing his body unto our fathers, and his mercy and long-suffering, and the hope of his glory and of eternal life, rest in your mind forever.
There has been a horrific scene of savagery unfolding before this families eyes. Hence the first line of this verse. Some watch R rated movies, others have to live inside them. To me it says despite the fallen nature of this world, despite the decisions of others, despite the condemned awful state of some, it does not prevent the individual from being lifted up by Christ. Faithfulness is to Him. In spite of all the barbary, Moroni was still able to commune with God, to receive inspired revelation, experiences, (Ether 12: 39) and write scripture. Mormon who is writing has an alternate set of thoughts he would like his son to have in his mind, as opposed to all the garbage in front of his eyes. It's interesting what vocabulary prophet to prophet communication has. The talk between them is very focused, very direct and very beautiful.
This father son moment, when father shares his life long wisdom, his ultimate wish for his son uses words such as "May Christ lift thee up... mercy and long-suffering, and the hope of his glory and of eternal life, rest in your mind forever." He wants such thoughts resting in his mind. Not post traumatic stress thoughts from war and savagery, which can weight down unto death, but thoughts of our Lord, hope, mercy, long-suffering, eternal life. He says may those things "rest in your mind". Such thoughts in my view put the mind at rest. What a thought rest is. To me it implies deep peace and tranquility. Eternal life is equated with knowing God. Having thoughts of eternal life resting in your mind no doubt is connected to thoughts of knowing God. I don't think rest is a vacation or retirement, or sitting around doing nothing. That gets old real fast anyway. But true rest. Rest that in chapter 7 He invites listeners to enter. What kind of physiological responses would such thoughts resting in ones mind have on the body? I think it would bring harmony, and peace. So we must calm our minds, let our fears and anxieties pass over us, make some room in our lives, hearts and minds, maybe evict the inner tenants, pride, or worry, or thoughts that do not belong. And instead ponder on truth, on light, on the Lord and His goodness, being ever willing to repent. I bet Mormon would have similar advice for any of his readers. He knows such thoughts can bring a soul ultimately to rest.