Matthew Henry wrote on this passage, "All who are chosen to happiness as the end, are chosen to holiness as the means." What he meant by these words is that the truly happy person in Christ is the one most committed to pleasing Him thru a life of devotion to holy things. This is not because they value piety or virtue in and of themselves, but because they love the Lord.
Jesus declared, in John 14:15, "If you love me, you'll keep my commandments." He wasn't saying that the proof of ones love for him is found in obedience (although true), but rather that one who truly loves Him will in fact walk in obedience as they strive for the holiness that pleases Him. Why? Because this is what love does - it strives to please the object of ones affections.
Because man is a fallen creature, his affections have been tainted and are naturally bent towards the self. And where selfish ambition exists, disorder and sinful living will follow (James 3:16). This is why one must be 'born again' in order to even understand where true happiness resides. And true happiness, according to the Scriptures, resides in knowing Christ and His salvation. Only here will one come to understand the meaning of life; the purpose of life; the goal of life; and the happiness of life in HIM! As the Apostle Paul once said, "To live is Christ and to die is gain." This doesn't mean that one enjoys life less... to the contrary it means that thru the pursuit of holiness, with Christ as the aim of one's affections, life can truly be lived to the full (John 10:10).
If you are growing in holiness in accordance with God's Word, and your heart bursts forth in love for the Savior... be sure of this: the God of The Universe is actively working in your life because you are HIS! Pray even now that God would conform you more and more into the image of the Holy One, the Lord, Savior, King, and Friend of those who believe on Him, the God-Man, Jesus Christ. For this is what He came to do - even your sanctification; and in Him you will truly be blameless and happy for all eternity.