The general theme of this section of Jesus’ discourse to the people in Bountiful has been the nature of their religious devotions. It began with instructions on the sacrament, and has not included admonitions to prayer and inclusiveness in communal worship. Just has Jesus originally addressed the information on the sacrament to the twelve, he now returns to focus on them, and on instructions for the sacrament. These specific instructions are appropriately given to the twelve as they are part of the administrative aspect of the gospel, and the twelve are those to whom the administration of the church and gospel will be given.
“To partake of the sacrament unworthily is to take a step toward spiritual death. No man can be dishonest within himself without deadening the susceptibility of his spirit. Sin can stun the conscience as a blow on the head can stun the physical senses. He who promises one thing and deliberately fails to keep his word, adds sin to Sin. On natural principles such a man "eats and drinks condemnation to his soul.” (Elder David O. Mckay, Conference Report, October 1929, First Day—Morning Meeting 14 - 15.)
Translation: Much of the language of this passage echoes Paul:
1 Corinthians 11:26-29
26 For as often as ye eat this bread, and drink this cup, ye do shew the Lord’s death till he come.
27 Wherefore whosoever shall eat this bread, and drink this cup of the Lord, unworthily, shall be guilty of the body and blood of the Lord.
28 But let a man examine himself, and so let him eat of that bread, and drink of that cup.
29 For he that eateth and drinketh unworthily, eateth and drinketh damnation to himself, not discerning the Lord’s body.
The 3 Nephi account is clearer than that of Paul, but the intent of both is the same. There is a responsibility that we each have to come to the sacrament in an attitude ready for repentance. If we are not so humble before the Lord, then we deny the very purpose of the sacrament, which is to remind us of the atoning mission of the Savior, and the provision of the conditions under which we may repent and improve. We need not, and probably cannot, be perfect as come to the sacrament. We can, however, be in an attitude of humility and willingness to follow the path of God if the atonement is applied to us so that we may progress.