Nephi's single-minded focus was life-long. Now, as he writes advanced in age, with a retrospective knowledge, and prophetic foreknowledge of revelation, he confirms what he has written is "of great worth." When a prophet like Nephi appraises the work as "of great worth," it is important to realize that your disagreement with the assessment is a reflection on you, not him. It is a reflection of your own level of understanding rather than on the work itself.
Are Nephi's two books "of great worth" to you? Why? Can you articulate the reasons they have this "great worth" in everything you think and do in your daily life? How have they changed you? If there is nothing you can point to of value, then perhaps you have not yet found the "great worth" Nephi believed his writing to hold.
Why "especially unto [Nephi's] people?" Who are Nephi's "people?" Why would they be more valuable to them? Why would they have a special value to them, above the value to the gentiles?
When Nephi says he "prays continually for them," who is the group he identifies as "them?" Why does he pray for "them?"
Why does Nephi cry into his pillow at night because of "them?" Who are they and what did Nephi know would be the end of "them?" (See 1 Nephi 12: 19; 1 Nephi 15: 5.)
Nephi knew his cries to the Lord would not go unheard. He knew the Lord would keep a covenant made with Nephi concerning "them." (1 Nephi 13: 30.) The remnant of Nephi's seed would not be utterly destroyed. Nevertheless, the future destruction would be near absolute, leaving only a remnant.
Despite this foreknowledge, Nephi nevertheless reports he made it a practice to nightly "cry unto my God in faith, and I know that he will hear my cry."
Nephi kept faith in the face of certain destruction of his descendants. Hope in the face of looming apostasy by his seed. Charity toward those who would reject the Lord.
He has ceased to be exclusively a prophet, and has risen to the role of intercessor and advocate for the unworthy. He has become covenantal father, and presiding Patriarch over a lineage whose redemption will come through his covenant with the Father. He has joined the ranks of the "fathers" toward whom hearts must turn in order to avoid cursing at the Lord's return. (Malachi 4: 6.)
The circle has closed and the eternal round is completed. Nephi has godly feelings and godly empathy for a doomed posterity. We behold at last the veil removed. We see such nobility of character, and greatness of soul that we are compelled to accept his role as teacher and ruler. He has taught righteousness all his days. Though his older brothers refused to acknowledge or accept him, we should not. His parting message suggests, however, that more of those who will read his record have the same spirit as Laman and Lemuel than will have the necessary spirit to recognize and "esteem of great worth" what he has provided to us.
It is almost too great to take in for the few who are the humble followers of Christ. However, they can avoid being led into error by recognizing in Nephi the teacher and ruler who was sent to deliver a message of salvation to a doomed people. For those who now live under the same prophetic doom, (3 Nephi 16: 15; 3 Nephi 20: 16; 3 Nephi 21: 12) Nephi represents a lifeline offered to those humble enough to accept his message. They will gladly recognize their plight, awake and arise and become people of prayer.