Scripture says of believers, “His divine power has given us everything we need for life and godliness through our knowledge of him who called us by his own glory and goodness” (2 Pet. 1:3). So what do we need to live righteously that He has not given us in Christ? Nothing.
The source of strength we call upon is not merely our own, which is insufficient, but God’s, which is infinitely powerful. God says, “My grace is sufficient for you, for my power is made perfect in weakness” (2 Cor. 12:9). You bring the weakness, He brings the power.
Does any of this imply that it doesn’t take a lot of effort to live the Christian life? Of course not. But notice the intertwining of effort in this partnership with God—“To this end I labor, struggling with all his energy, which so powerfully works in me” (Col. 1:29). We must make every effort to be righteous, to obey Him, to avoid sinful thoughts and actions. Yet all the while we must do this appealing to His strength, not our own.
One caution is important here. Some people approach the concept of “allowing God to work through me” as if it were some passive condition whereby God invades you and takes over, automatically causing you to live righteously, bypassing your own will. Not true. The spiritual life is warfare. To win the fight you must take on the armor of God and wield the sword of God’s Word, which requires diligence and hard work (Eph. 6:10-18). As J. I. Packer says in his book Keep in Step with the Spirit, “The Christian’s motto should not be ‘Let go and let God’ but ‘Trust God and get going!’”
There is no contradiction between God working in you and you working to follow God. This is the nature of the spiritual partnership He establishes with us. He works, and so must we. If you pray that God will keep your thoughts sexually pure, then turn around and look at pornography, you act in contradiction to your prayer, showing it to be only words. You must demonstrate that you are serious about your prayer by taking all the steps to avoid sexual immorality of the mind and body. In other words, it matters what you do.