How do we have victory over the world, the flesh, and the devil?
With watchfulness through the power of the Holy Spirit.
Catechism for the Global Methodist Church, question 76
16You shall not test the LORD your God, just as you tested him at Massah. 17You shall diligently keep the commandments of the LORD your God and his testimonies and his statutes that he commanded you. 18And you shall do what is right and good in the eyes of the LORD, so that it may go well with you and you may come in and possess the good land that the LORD swore to your fathers, 19to drive out all your enemies from before you, just as the LORD has spoken.
36About that day and hour no one knows, neither the angels of the heavens nor the son, except the father alone. 37For just as the days of Noah were, so will be the coming of the son of a human. 38For as they were in the days before the flood, eating and drinking, marrying and giving in marriage, until the day when Noah entered the ark, 39and they did not know until the flood came and took them all away, so will be the coming of the son of a human. 40Then two will be in the field; one is taken and one is released. 41Two will be grinding at the millstone; one is taken and one is released. 42Keep watch therefore, for you do not know on what day your lord comes. 43But know this, that if the householder had known in what watch the thief was coming, he would have kept watch and would not have allowed his home to be broken into. 44Because of this you also must be ready, for at an hour you do not think the son of a human comes. 45Who then is the faithful and thoughtful slave whom the lord appointed over his household to give them their food at the proper time? 46Blessed is that slave whom his lord, when he comes, will find so doing. 47Amen I say to you that he will appoint him over all his possessions. 48But if that evil slave should say in his heart, 'My lord delays,' 49and should begin to strike his fellow slaves, and to eat and drink with those who get drunk, 50the lord of that slave will come on a day when he does not look for him and at an hour he does not know, 51and will cut him in two and assign his part with the hypocrites; there will be weeping and gnashing of teeth.
1Then the kingdom of the heavens will be likened to ten virgins who, having taken their lamps, went out to meet the bridegroom. 2Five of them were foolish and five were thoughtful. 3For the foolish, having taken their lamps, did not take olive oil with them. 4The thoughtful, however, took olive oil in jars along with their lamps. 5While the bridegroom delayed, they all became drowsy and fell asleep. 6At midnight a shout arose: Look! The bridegroom! Go out to meet him. 7Then all those virgins got up and trimmed their lamps. 8The foolish said to the thoughtful, Give us some of your olive oil, because our lamps are going out. 9The thoughtful replied, There may not be enough for us and for you; go instead to the sellers and buy some for yourselves. 10While they went to buy, the bridegroom arrived, the ready ones entered with him into the wedding, and the door was closed. 11Later the other virgins arrived and said, Lord, lord, open to us. 12He answered, Truly I say to you, I do not know you. 13Watch therefore, because you do not know the day or the hour.
34But watch yourselves lest your hearts be weighed down with dissipation and drunkenness and the worries of this life, and that day come upon you suddenly. 35For it will come upon all those who dwell on the face of all the earth like a trap. 36But keep awake at all times, praying that you may have strength to escape all these things that are about to take place, and to stand before the Son of Man.
13Therefore, having girded up the loins of your mind, being completely sober, set your hope upon the grace that is being brought to you at the revelation of Jesus Christ. 14As children of obedience, do not be conformed to the desires that once governed you in your ignorance, 15but, as the one who called you is holy, become holy yourselves in all your conduct. 16For it is written, 'You shall be holy, because I am holy.'
8Be sober; keep watch. Your opponent the devil, as a roaring lion, walks seeking someone to swallow. 9Oppose him, strong in the faith, knowing that the same sufferings are being completed in your brotherhood throughout the world.

This question closes the catechism's treatment of entire sanctification with the last sentence of Article XI of the Confession of Faith: "Thus he rules over these enemies with watchfulness through the power of the Holy Spirit." The answer joins a human posture, watchfulness, to a divine power, the Spirit. The believer is to watch and pray, and the victory belongs to God.
Watchfulness is one of the New Testament's steadiest commands, and the catechism gathers its main texts. Jesus tells his disciples, "Keep watch therefore, for you do not know on what day your lord comes" (Matthew 24:42). The ten virgins of Matthew 25 all fell asleep, and the difference between them was the oil they had prepared beforehand: "Watch therefore, because you do not know the day or the hour" (Matthew 25:13). Luke gives the remedy: "keep awake at all times, praying that you may have strength" (Luke 21:36). Peter addresses the devil by name: "Be sober; keep watch. Your opponent the devil, as a roaring lion, walks seeking someone to swallow. Oppose him, strong in the faith" (1 Peter 5:8-9). Deuteronomy adds that the watchful life is a life of obedience, keeping "the commandments of the LORD your God and his testimonies and his statutes" (Deuteronomy 6:17) so that the Lord himself will "drive out all your enemies from before you" (Deuteronomy 6:19).
Through the power of the Holy Spirit keeps the Christian from mistaking watchfulness for self-reliance. Peter's exhortation to holiness begins with a mind girded and sober and a hope set "upon the grace that is being brought to you" (1 Peter 1:13). The holiness is commanded, "become holy yourselves in all your conduct" (1 Peter 1:15), and the grace that makes it possible is given. ΒΆ102.2 of the Book of Doctrines and Discipline defines grace itself as "the active, empowering presence of God, through the Holy Spirit, enabling believers to trust, love, and serve God."
For a Methodist, victory over the world, the flesh, and the devil is a daily practice rather than a single event. It looks like the examined conscience of the old class meeting and prayer kept up when it would be easier to let it lapse. The power in all of this is the Spirit's, and the watchfulness is the believer's way of staying where that power is at work.