God never said that the righteous would not suffer. In fact, he said quite the opposite. The Lord said that those who love him will suffer greatly: “we must through much tribulation enter into the kingdom of God.” (Acts 14:22) He said that the servant is not above the master, and that we should not be surprised when the world treats us the same way it treated him:
Remember the word that I said unto you, The servant is not greater than his lord. If they have persecuted me, they will also persecute you... (John 15:20)
Suffering increases with righteousness. Paul described the suffering of those who were so righteous the world “was not worthy” of them:
35 ...others were tortured, not accepting deliverance; that they might obtain a better resurrection:
36 And others had trial of cruel mockings and scourgings, yea, moreover of bonds and imprisonment:
37 They were stoned, they were sawn asunder, were tempted, were slain with the sword: they wandered about in sheepskins and goatskins; being destitute, afflicted, tormented; (Hebrews 11)
The more righteous a person, the more the wicked will hate and persecute them, and the greater their suffering will be. Similarly, the more righteous a person, the more willing they will be to suffer greater things for the benefit of others.
While the righteous suffer greatly, they do not suffer in the same ways as the wicked. They enter into suffering because they are willing to do what is right, while the wicked suffer because they are unwilling to do what is right. Consequently, the righteous are both spared from all unnecessary suffering and they are given all strength and power through faith in Christ to overcome all suffering.
For whatsoever is born of God overcometh the world: and this is the victory that overcometh the world, even our faith. (1 John 5:4)
The righteous will avoid all unnecessary suffering through keeping God’s commandments. In faith, God also provides the righteous with the greatest support possible to enable them to endure suffering which cannot be avoided in their journey towards the knowledge God possesses.
And the Lord provided for them that they should hunger not, neither should they thirst; yea, and he also gave them strength, that they should suffer no manner of afflictions, save it were swallowed up in the joy of Christ. Now this was according to the prayer of Alma; and this because he prayed in faith. (Alma 31:38)
Having afflictions “swallowed up” does not mean they don’t exist. It doesn’t mean they don’t cause extreme pain. As evidence of this point, consider that the same phrase is used to describe how resurrection saves the faithful from the finality of death:
But there is a resurrection, therefore the grave hath no victory, and the sting of death is swallowed up in Christ. (Mosiah 16:8)
Many righteous people have and will die. Yet, faith in the mission, character, and teachings of Christ change a faithful person’s experience in death. Those who die with faith in Christ do not experience the bitterness felt by those who do not have faith:
`...they never did look upon death with any degree of terror, for their hope and views of Christ and the resurrection; therefore, death was swallowed up to them by the victory of Christ over it. (Alma 27:28)`
The sting of death is “swallowed up” by their understanding of how their experience—no matter how painful—is for their benefit:
...the sufferings and death of Christ atone for their sins, through faith and repentance...breaketh the bands of death, that the grave shall have no victory, and that the sting of death should be swallowed up in the hopes of glory.... (Alma 22:14)
“Swallowed up in Christ” means that faith in Christ can provide a counterbalance to the pain. It means that, through Christ, the afflictions can be made worthwhile.
Only the righteous will possess the requisite purpose to find joy in the midst of the greatest of suffering.
Unlike that of the wicked, whose suffering will continue until they learn from it, the suffering of the righteous ends when justice is meted out by God: “Many are the afflictions of the righteous: but the Lord delivereth him out of them all.” (Psalm 34:19)
The exercise of faith actually contributes to the joy one obtains after walking the path of godly suffering, as the retrospective awareness that you pushed forward based only on faith provides you with joyful satisfaction in what you have obtained. It is the confidence that you remained fully faithful to God at all hazards that gives you the “boldness to enter into the holiest by the blood of Jesus.” (Hebrews 10:19) It is your willingness to suffer—"to submit to all things which the Lord seeth fit to inflict upon [you], even as a child doth submit to his father” (Mosiah 3:19)—that gives you “a conscience void of offence toward God, and toward men.” (Acts 24:16) Your willingness to endure all necessary suffering through faith in Christ gives you “boldness and access with confidence by the faith of him.” (Ephesians 3:12) Through following the example of Christ “at all times and in all things, and in all places” (Mosiah 18:9)—through any suffering that might require, even if it requires your life—you will “have boldness in the day of judgment: because as he is, so are we in this world.” (1 John 4:17)