Do you ever worrying about things you can't control? I find myself in a frequent state of anxiety, worrying about things that (more often than not) never happen. I often pray and "give" these situations to God, but then I unintentionally take them back, thinking I have the answer.
God's word specifically tells us that we should not be anxious. It commands us to pray about everything with thanksgiving. When you're in a losing season or a failing marriage, or you are grieving the loss of a loved one, it's difficult to be thankful. It's much easier for all of us to ask God why we're going through these battles and then tell Him what we think He ought to do to remedy the situation. Only when we allow Him to have total control will we find peace in our lives.
As believers in Christ, we are supposed to be a source of encouragement to others. We cannot do this when our thoughts are focused on things that keep our hearts in turmoil. Philippians 4:8 doesn't mention any of the things that cause us anxiety; however, the verse lists some wonderful traits for us to dwell on: the things that are true, honorable, right, pure, lovely and admirable.
As you go through your day today, intentionally make God your number-one priority. Build every aspect of your day around your relationship with Him. Live each moment focusing on the things that are true (not the gossip you heard at practice), honorable (not the lies that you convince yourself are truth), right (the absolutes, not the gray areas that you often try to make right), pure (not corrupt), lovely (things that make God smile), and admirable (things that will please God and improve your reputation as a follower of Christ).
If you're thinking on the things in verse 8, I can assure you that there will be no room in your head or your heart for anxiety.