Do you remember the “just say no to drugs” campaign waged a number of years ago? (The slogan “just say no” continues to be used in schools across the country.) The assumption of the slogan was that kids could simply say “no” whenever faced with temptation. Is that true? Can we simply say “no” whenever we are tempted?
There is a significant difference between a believer and an unbeliever who tries to answer this question. An unbeliever is utterly stuck in sin. Granted, the unbeliever can clean up a behavior he views as wrong, but is that really house cleaning? Such “cleaning” is no more than moving piles from one room to another so the guests can’t see the mess.
The unbeliever’s attempt to overcome sin reminds me of the children’s arcade game where you have to hit with a huge mallet whatever blue furry head pops up. The problem with trying to deal with temptation simply by hitting it down is that the moment an unbeliever hits one popping-up head, another pops up behind or in front of him. The unbeliever simply does not have the means by which to consistently overcome sin because he or she has not been indwelt by the Spirit.
But one who has come into a right relationship with God by receiving God’s gift of grace through faith and who has been indwelt by the Spirit of God has been given whatever is needed to overcome a given temptation (1 Cor 10:13). “Whatever is needed” is no less than the presence and power of God’s own Spirit! And this is what we have received if we truly know him (Rom 8:9-11).
So how should we cooperate with what the Holy Spirit is trying to do to sanctify us? Galatians 5:16 offers a straightforward answer: “But I say, walk by the Spirit, and you will not gratify the desires of the flesh.” Walking by the Spirit and carrying out the desires of the flesh are mutually exclusive ideas; you are either walking by the Spirit or carrying out the desires of the flesh. You can’t do both at the same time. In short, you need to learn how to walk in the Spirit.
Simply saying “no” to sin is like trying to remove all of the air from a cup by covering it with a plastic lid and trying to suck out the air with a straw. You can’t get it all out, even if the lid is well sealed—which it isn’t if you are an unbeliever. But if your goal really is to remove all the air from a cup, fill it up with water and you can be certain that all the air will be out! (Side note: water is one of many biblical metaphors for the Spirit, John 7:38-39). If you really want to overcome sin, then learn the pattern of living life in step with the Holy Spirit (Gal 5:16; Rom 8:4), being filled with the Spirit (Eph 5:18), and setting your mind on the things of the Spirit (Rom 8:5-8). The result of such “walking” will be a realization of the power you need to put to death the deeds of the body by the Spirit (Rom 8:12-13).
There is more to be said about overcoming sin than what I’ve written here, but today I wanted to focus on this one key component. It is a vital message for a church culture that tends toward simplistic moralism and does not often stress what the Bible accentuates about overcoming sin by walking in step with the Spirit.
 For more interaction on overcoming sin by the Holy Spirit, see Kenneth Berding, Walking in the Spirit (Crossway, 2011), chapters 1-3.