Elder David A. Bednar talks about the two groups in Lehi's vision who held on to the iron rod and made it to the tree of life.
"It is significant that the second group pressed forward with faith and commitment. They also had the added blessing of the rod of iron, and they were clinging to it! However, as they were confronted with persecution and adversity, they fell away into forbidden paths and were lost. Even with faith, commitment, and the word of God, this group eventually was lost - perhaps because they only periodically read or studied or searched the scriptures. Clinging to the rod of iron suggests to me only occasional "bursts" of study or irregular dipping rather than consistent, ongoing immersion in the word of God.
In verse 30 we read about a third group of people who pressed forward continually holding fast to the rod of iron, until they came forth and fell down and partook of the fruit of the tree. The key phrase in this verse is continually holding fast to the rod of iron.
...Perhaps it was the spiritual nourishment and strength provided by continually feasting upon the words of Christ that enabled this group to heed not the scorning and mocking of the people in the great and spacious building. This is the group you and I should strive to join."