Verse 12 begins with a result, that is, a result David longs to see accomplished in the lives of the children of Israel. To paraphrase, he is saying, 'When the bad guys are defeated, then we can have peace. Then our sons and daughters can grow up in peace and not have to fight such battles. Then we will be financially blessed which is being described by the animals increasing in numbers (verse 13). Then nobody we know will be taken in to captivity and no one will be in distress (verse 14).' These verses are about a wish of the day where life can be peaceful and the blessings of God are upon the people.
Will this day ever come for the children of Israel? In David's case, he had to fight wars all of his life. By the time his son Solomon came to power, Israel was at peace with their enemies and the people of Israel could live this way. The mistake Solomon made was that he started trusting in everything other than God and eventually God removed the blessings that had resulted from David's battles.
So does that mean we should never wish for the type of life that Solomon had when the nation of Israel was blessed greater than any country in history? To put it in perspective, think of it this way. David is spoken of highly in the New Testament and in the Old Testament books written after his life. Solomon was thought of as someone who blew it. Jesus' only comment on Solomon's glory is that the "lilies of the field have greater glory than Solomon at the peak of his power. (see Matthew 6:28-30).
Should we desire David's dream in these verses? Does God ever give us a time in our life where everything is wonderful and there are no problems? We can always think of reasons to be grateful to God and we can always think of problems in the world around us. I guess a question for all of us to consider at any one time is do we want to focus on joy, or do we want to focus on our problems? Yes our problems are real and still right in front of us. However, we can have peace through our difficult times if we focus on the One who is the source of our peace.
David essentially wanted life to be good and not have anything to worry about. I suspect the true answer to David's request in these verses only comes with our attitude and our trust in God. Again, David's children did get to see a world of relative peace like David desired, and yet the problem is when one experiences a world like that, one tends to trust in that peace instead of trusting in the God who provided that peace in the first place. Therefore, my answer to this question of receiving the things David desired in these verses comes from our attitude and our perspective about God and not what we actually receive in this lifetime.
 Happy is that people, that is in such a case: yea, happy is that people, whose God is the LORD. This final line gives the answer to David's request of peace, prosperity and happiness. It is not about those who actually receive lots of financial blessings. Blessings in this life come from those who actually trust in God and let go of one's worries. Then we are blessed far greater than by all of the "stuff" listed in the previous set of verses in this Psalm.