"Do all things without grumbling or disputing; so that you will prove yourselves to be blameless and innocent, children of God above reproach in the midst of a crooked and perverse generation, among whom you appear as lights in the world, holding fast the word of life, so that in the day of Christ I will have reason to glory because I did not run in vain nor toil in vain. But even if I am being poured out as a drink offering upon the sacrifice and service of your faith, I rejoice and share my joy with you all. You too, I urge you, rejoice in the same way and share your joy with me." (Philippians 2:14-18)Paul had just exhorted the Galatians to obey him, not only when he was present, but "but now much more in my absence." (Philippians 2:12) Here Paul gives some examples of the things he had commanded them to obey: do not grumble, stop fighting with each other, etc. The things Paul commanded the Galatians to obey are the same kinds of things a parent would instruct their children to do: do not lie, play nice with each other, don't fight, etc. Paul's relationship with the Galatians was not as an overload but as a father.
It is interesting that the way we prove ourselves to be children of God not through the purity of belief or our fidelity to a statement of faith but through our actions that show we have learned to conform our lives to the pattern set for us by our heavenly Father. Our conformance to creeds proves ourselves to be children of religion but our obedient behavior to our Father proves ourselves to be children of God.
It was said of Jesus that, "In Him was life, and the life was the Light of men." (John 1:4) The light of Jesus was not His creed or statement of faith but it was the life He lived. The life Jesus lived showed us a new reality, a new way to live. It showed us that it was possible, through God's help, to live a righteous life, a life that was new, abundant, and free of sin. The same is true today of our lives. If we live as children of God, then our lives will be the light of men; showing them the new life that is possible in Christ. This is why Jesus described us saying, "You are the light of the world. A city set on a hill cannot be hidden; nor does anyone light a lamp and put it under a basket, but on the lampstand, and it gives light to all who are in the house. Let your light shine before men in such a way that they may see your good works, and glorify your Father who is in heaven." (Matthew 5:14-16)
Paul's mission in life was not to teach people but to deliver them to God as children of their heavenly Father. This meant not only seeing them united with the Father but also being conformed into His image and into the image of His Son. The proof of this transformation was to be evident in how they lived their lives. In Galatians, Paul speaks of running in vain regarding his gospel, "I submitted to them the gospel which I preach among the Gentiles, but I did so in private to those who were of reputation, for fear that I might be running, or had run, in vain." (Galatians 2:2) However, here he speaks of having run in vain in regards to his mission, the mission of seeing those he ministered to becoming transformed into the image of Christ.
Paul found the secret to joy, even when faced with personal challenges and difficulties. Paul's joy was in seeing the positive effect of his ministry happen in the lives of other people. Paul did not live for his own benefit but found joy when his life brought benefit to others. When we live for ourselves, it is easy to become angered when circumstances do not turn out the way we had hoped and when difficulties and disappointments flood our lives. Our anger robs us of our joy and saps the strength of our life. However, when we live for the benefit of others, then even our circumstances are seen as opportunities to benefit others by allowing God to show Himself strong in the midst of our difficulties that others may take hope and increase in faith. Paul encourages us that this approach to life ought also to be ours; that in living for others we too might share in the same joy that Paul found in his service to others. Such a life is contrary to the world, but is rewarding in Christ.