We are commanded to humble ourselves before our Lord, letting Him be Lord of our lives. As a part of humbling ourselves, we are to cast all of our cares upon Him, not just because He has the power to solve those problems, but because he does care for us.
However, if we don't humble ourselves to let go of our problems and let the Lord handle them, we can be subject to spiritual attack of the most severe kind, for our enemy the devil seeks to devour us. Thus, we must always be on the alert.
This spiritual warfare should not be anything to discourage us or to cause us to lose our resolve, for we do have the strength in Christ to resist the enemy. We are commanded to resist the enemy here in this passage, and Philippians 4:13 clearly states that we can do all things through Christ who strengthens us. We know that other people are facing the same things now. Not only so, but others have faced the same trials in the past; who are we to say that the God who carried them through their trials cannot carry us through our own trials now?
What does the Lord desire to bring about in our lives as a result of these trials? Take a look at the passage, in verse 10. The author, Peter, must have been quite excited by the time he got finished with this passage, for he ends it with an exclamation... see verse 11.
Hang in there!