If, Then
This past Sunday morning, Phil Johnson preached on Psalm 127:1-2 in church.  He made the point that this psalm may have been written by Solomon or by David for Solomon, and that there are similarities between that psalm and many of the proverbs.
I was struck by similarities between Psalm 37 and many of the proverbs, also. 
This time I will focus on verse 4:  Delight yourself in the LORD; and He will give you the desires of your heart.
That is certainly straightforward enough:  if I delight myself in the LORD, then He will give me the desires of my heart.
How could I count on that?  If I delight myself in the LORD, my desires will come into alignment with His and therefore He will have no problem giving me the desires of my heart.
This is how sanctification is worked out in the life of the believer:  work out your salvation with fear and treambling; for it is God who is at work in you, both to will and to work for His good pleasure (Philippians 2:12b-13).