Col 1:29 “To this end I also labor, striving according to His working which works in me mightily” for “13 for it is God who works in you both to will and to do for His good pleasure”, Phi 2:13.
The marvelous work of God is mostly displayed in the backdrop of our weakness. Our weakness turns us to God’s sufficient power of both to will and to do. Paul declares that he is laboring (working) but he avows that he has power to “strive” in the spirit for his converts only as Christ works in him and by him.
Paul resolved to never lean on self but on the sufficient power of God to save and keep. Paul accredits to God Effectual calling (justification) and Effectual living (sanctification). They are all under the umbrella of the effectual working.
According to the working. Christ within us is a life and a power. If we conquer the flesh and give ourselves entirely up to him he will work mightily. Act 17:28 “for in Him we live and move and have our being …”, 2Co 13:4 “For though He was crucified in weakness, yet He lives by the power of God. For we also are weak in Him, but we shall live with Him by the power of God toward you”