Psalm 3 (NASB)
1 O LORD, how my adversaries have increased! Many are rising up against me. 2 Many are saying of my soul, "There is no deliverance for him in God. 3 But You, O LORD are a shield about me, My glory and the One who lifts my head. 4 I was crying to the LORD with my voice, and He answered me from His holy mountain. 5 I lay down and slept; I awoke, for the LORD sustains me. 6 I will not be afraid of ten thousands of people who have set themselves against me round about. 7 Arise, O LORD; save me, O my God! For you have smitten all my enemies on the cheek; You have shattered the teeth of the wicked. 8 Salvation belongs to the LORD; Your blessings be upon Your people!


Reading this Psalm in context makes me think that my life is so easy... David was running for his life, from his son when he wrote this Psalm.  So to him, I'm sure the world seemed completely against him. I know, even though it's nothing compared to what David was feeling, that sometimes I feel like the world is at odds with me. However, what I appreciate about this is the response, God is my shield, He keeps my head up, He answers me and ultimately...I can sleep peacefully at night, no matter the circumstances.  This Psalm is filled with promises of God's strength and power. 
The other part of this Psalm that stuck out is the imagery of how the enemies are dealt with, it seems to describe a close up fight...hand to hand and the enemy is beat up, struck to the face with broken teeth. That's a pretty great description! This Psalm is a promise to fall back on when it feels like the world isn't for you, God is!