Gal. 2:19 For when I tried to keep the law, I realized I could never earn God's approval. So I died to the law so that I might live for God. I have been crucified with Christ.
The Apostle Paul did not always have it right. There was a time in his life in which he really tried hard to please God by obeying the law of God. He was driven to excel in law keeping and he was respected by his peers because of his zeal. He was a Pharisee and had risen to the top in his day. He was widely recognized as a very religious man. Yet, Paul knew that he wasn't good enough. Deep in his soul he knew that he could never be good enough.
Paul knew the Scriptures. He knew them better than most and he knew that no matter how hard he tried, he always came up short. He couldn't meet his own expectations for godly living, let alone God's. He knew there had to be something missing in his understanding and life.
When Paul had his encounter with Christ on the road to Damascus, his life was forever changed. Jesus opened his eyes so that he could understand that He was the fulfillment of the law Paul was so obsessed by. Paul understood for the first time that Jesus is our righteousness, not what we do. Paul understood that apart from Christ he would never gain God's approval. So, Paul changed his ways.
Instead of trusting in his efforts, Paul put his trust in Christ and discovered what it was to have a living relationship with God. He became a totally different man. Christ set him free from himself so that he could now be made holy in God's eyes. As with Paul, so it is with us. Christ, and Christ alone, is our righteousness. He alone makes it possible for us to be children of God, both now and forever.