training us to renounce ungodliness and worldly passions, and to live self-controlled, upright, and godly lives in the present age
Even in sections of theology like this one, Paul cannot refrain from disclosing doctrine’s application. Here the emphasis is that the gospel trains us in godliness. In believing the truth of Scripture, we must conform ourselves to the pattern of life that it outlines.
This means that we renounce, or reject, ungodliness and worldly passions. Our passions are, instead, upon the things of God. In fact, Peter goes so far as to claim that worldly and fleshly passions ‘wage war against your soul (1 Peter 2:11).”
Thus, the battle over what we desire is exactly that—a battle.
Whether for war, athletics, or other things, training is difficult; it’s a fight. It requires discipline and work, and spiritual training is no different. Anyone who has spent any length of time in prayer, fasting, and the study of the Scriptures will readily verify the strenuous nature of the growing in godliness.
Fortunately, we can always rely upon the truth that the Jesus’ grace is entirely sufficient (meaning we now work from gratitude, not obligation) and that God is training us (He is our coach).
Or we could say it like this: though we are called to work hard, we can only do so because God worked first in us and continues to work through us.
With this in mind, we would do well to remember that spiritual warfare is not merely waged over what we do but also what we want. Our desire must be to live lives that are pleasing to the One who graciously saved us.