When Paul says to put to death the deeds of the body “by the Spirit” (Romans 8:13), I take him to mean that we should use the one weapon in the Spirit’s armor that is used to kill. Namely, the sword. Which is the word of God (Ephesians 6:17).
So when the body is about to be led into a sinful action by some fear or craving, we are to take the sword of the Spirit and kill that fear and that craving. In my experience that means mainly severing the root of sin’s promise by the power of a superior promise.
So, for example, when I begin to crave some illicit sexual pleasure, the sword-swing that has often severed the root of this promised pleasure is: “Blessed are the pure in heart, for they shall see God” (Matthew 5:8). I recall the pleasures I have tasted of seeing God more clearly from an undefiled conscience; and I recall the brevity and superficiality and oppressive aftertaste of sin’s pleasures, and with that, God has killed the conquering power of sin.
It is a beautiful thing to be the instrument of God’s word-wielding power to kill sin.
Having promises at hand that suit the temptation of the hour is one key to successful warfare against sin. But there are times when we don’t have a perfectly suited word from God in our minds. And there is no time to look through the Bible for a tailor-made promise.
So we all need to have a small arsenal of general promises ready to use whenever fear or craving threaten to lead us astray.
Read about the weapons at Desiring God