"And when the Chief Shepherd appears, you will receive the crown of glory that will never fade away." NIV translation
This verse refers to Moses and how the glory of God caused his face to shine but it faded (see Exodus 34:29 - 35). When Christ comes back, the glory will be with us but it will never fade. This verse reminds us that the elders answer directly to the Chief Shepherd which is Jesus.
"Young men, in the same way be submissive to those who are older. All of you, clothe yourselves with humility toward one another, because, 'God opposes the proud but gives grace to the humble.'" NIV translation
Now Peter moves from teaching the elders to teaching the rest of the people.
He reminds the young to submit to the authority of the elders. It is important to note here that Peter is not simply talking about those who are older in years but is talking about those that are older and more mature in the faith.
Then, he quotes from Proverbs 3:34 and contrasts grace and pride. A good example of this contrast is found in Esther 5.
"Humble yourselves, therefore, under God's mighty hand, that he may lift you up in due time." NIV translation
God not only gives grace to the humble as we saw in the previous verse but he will also lift you up. He will lift up the humble because that brings out God's glory. When the proud lift up themselves it is for their own glory and that is not of God but of Satan.
"Cast all your anxiety on him because he cares for you." NIV translation
We do not have to worry when we give things over to God. El Shaddai is big enough to handle anything and He loves His children. Jesus told us, in Matthew 6:25-34, that our Father will take care of us and there is no need for anxiety (worry).
"Be self-controlled and alert. Your enemy the devil prowls around like a roaring lion looking for someone to devour." NIV translation
We need to be on our guard so that we can recognize the work of the devil and resist the temptations that he will put in our path. If you are in Christ, he is your enemy and is out to destroy you. Satan is at work in this world and will use people and things to try to separate you from God. We can rejoice even in this because the Spirit of God living in us is greater than the devil. The devil may roar like a lion but he does not have the teeth (power) of the lion. Jesus is the Lion of the tribe of Judah and Satan is the big counterfeit (see Revelation 13).