The optimal policy to prepare for eternity is exactly the same as the optimal policy for living a good life here and now.
Russell M. Nelson, the prophet and president of the Church of Jesus Christ of Latter-day Saints, recently taught:
Here is the great news of God’s plan: the very things that will make your mortal life the best it can be are exactly the same things that will make your life throughout all eternity the best it can be!
(Think Celestial! October 2023 General Conference)
In the same talk, he says:
Far too many people live as though this life is all there is.
If we take the shortsighted view, we might assume this not to be true (because he appeals both to the idea that taking an eternal view is optimal and stating that one can live one's true best life now, and that these are equivalent and mutually satisfiable), but in reality there is no contradiction. The difference is made in one's perspective and the consequences that follow from taking "the long view" rather than thinking only of today.
One's policy choices can either discount the reality of tomorrow, or they can take tomorrow into account. More generally, we can regard the future--including the next few moments or hours--or we can choose not to think of it. The differences of perspective here lead to very different choices and outcomes.
The realization that taking an eternal view in fact results in the best and most personally rewarding policy choices today is emergent from experience, and has even been recognized from purely mathematical and secular perspectives.
This is well illustrated in the classic mathematical problem known as the Prisoners' Dilemma. A video explanation of the problem can be found here.
In the usual initial statement of the problem, it is apparently rationally ideal for the two prisoners to betray each other, because neither one is certain of the other's choice. However, the actual ideal for everyone is to choose virtuous cooperation. This becomes more evident as the experiment is repeated through a series of successive trials or engagements.
Note that it is not necessary for eternity to be accepted as reality or even to be a reality for this finding to hold; rather, it is a sufficient condition for the emergence of perfectly rational cooperation as the provably optimal policy when the test is of a finite duration only involving multiple encounters. This becomes even more strongly the case when the duration is not known in advance.
None of the participants in this dilemma even needs to know that there is a tomorrow, but when all participants act as though there is a tomorrow, and treat future outcomes as at least somewhat relevant to today, it results in optimal choices today.
This dilemma is also explored in a video by Veritasium, in which it is revealed by professors who studied the phenomenon further that an emergent, perfectly rational and optimal policy for such encounters includes five foundational virtues:
- Kindness (not giving the first offense, see Alma 48:14)
- [Measured] Retaliation or Restitution ("an eye for an eye, tooth for a tooth", Exodus 21:22-24, see also Alma 43:47)
- Forgiveness (Matthew 6:14-15, etc.)
- Clarity (Scripture clearly spells out concrete examples of one's own policy in the form of commandments and the Beatitudes)
- Generosity (this accounts for noise or incorrect perceptions, including notably the precept of "innocent until proven guilty beyond all reasonable doubt"; see Deuteronomy 19:15, John 8:7, etc.)
All of these principles are founded in and taught by Christianity, but they are not exclusive to a belief system that includes eternity and final judgment.
(Note that in the video, the professor erroneously states that the optimal policy "isn't Christianity", because it isn't "turn the other cheek", making it a "pushover" that is easily taken advantage of. However, this conveys a misunderstanding of what Christianity is; the God of the Old Testament and the God of the New Testament are one and the same, and His religion includes elements both of retaliatory justice through boundaries and of kindness, forgiveness and generosity. Christianity is also the oldest religion, being taught to Adam and Eve. "Turn the other cheek" can also be thought of as a generous policy, which they outline as another latent rationally optimal choice that is necessary to temper the role of misperception in an otherwise suboptimal scenario of escalatory retaliation).
While the exact tuning and appropriate application of these parameters will depend in some degree upon the kind of company one is surrounded by, the principles must remain in order for the policy to be robust against manipulation. Doctrine and Covenants section 98 spells out a policy that includes all of these elements of kindness, forgiveness, retaliation, and generosity, in a very clear and enumerated fashion.
Scripture teaches that even in the moment,
Wickedness never was happiness. (Alma 41:10)
In summary, the mathematically proven optimal policy for living your best life and obtaining the best outcomes today is already included in the teachings of Jesus Christ, and even mathematicians agree that taking only the conditions of mortal life into account, these virtuous principles form the basis of all the best policies and result in superior outcomes to more limited, shortsighted and unkind policies.
all things whatsoever ye would that men should do to you, do ye even so to them: for this is the law and the prophets
(Matthew 7:12)