Notice the progression from clouds, to rain, to vegetation. The Lord attends to every aspect of the world which He created. The thought being that God not only cares for human kind but He is intricately involved in our planet so that it "works". The psalmist has moved from discussing the stars in the sky down to the smaller scale of thinking about our specific planet. If one has nothing else to be grateful for in life, one can appreciate how God created our planet, so that it sustains life.
No matter what any of us do, clouds will form so that rain comes down and grass will then grow. That grass provides food for animals.
 He giveth to the beast his food, and to the young ravens which cry.
What is the deal with "young ravens" in verse 9? There is an ancient belief that ravens abandon their children and those raven children have to survive on their own. Remember that Jesus Himself said that God provides for these ravens. (See Luke 12:24). Obviously, the point is not to understand about cows and ravens. The point is to appreciate this world that God has created and His ability to sustain life here.
 He delighteth not in the strength of the horse: He taketh not pleasure in the legs of a man.
We continue to work our way from a big view of our world down to a smaller scale in each of these verses. The point here is to consider the strength of some strong animals or the strongest muscles in our own bodies, our legs. Obviously, that does not mean we can't use any of our muscles or use these animals. This comes back to the idea that in order to make a difference for God, He delights in those of us who trust in Him with our lives.
 The LORD taketh pleasure in them that fear Him, in those that hope in His mercy.
God seeks to intervene on behalf of those who fear Him. Think of it this way; do the armies that are best equipped or are the largest always win battles? Not that I have observed. The point is that God desires to guide our lives and He can give us victories in situations that appear to be sure losses without His help.
This doesn't mean we win every battle we face in life. It means that over time, God's will gets done and He uses people in order to accomplish His will.