In this nine minute presentation, covering 1 Peter 2:7-12, we can see that as Peter had begun his letter with the glorious truths of salvation, of the profound alteration believers experience, having put their faith in Jesus and been transformed by the divine work of the Holy Spirit, there is also a purpose.
Along with the great privilege of salvation comes the responsibility to grow in holiness, so that being born anew, believers now crave the pure spiritual milk of the word, are built up into the house of God, mature in faith, and serve God.
There is another component of Christian maturity:
Conduct yourselves honorably among the Gentiles, so that, though they malign you as evildoers, they may see your honorable deeds and glorify God when he comes to judge.1 Peter 2:12 (NRSV)
Embedded in this instruction is something of what the Apostle Paul called on all Christians to consider:
I appeal to you therefore, brothers and sisters, by the mercies of God, to present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship. Do not be conformed to this world, but be transformed by the renewing of your minds, so that you may discern what is the will of God—what is good and acceptable and perfect.Romans 12:1-2 (NRSV)