What does it mean to overcome in Revelation?
To overcome in Revelation means that a believer, armed with the Spirit of God just as Christ was, has already won the victory over the world, sin, and the power of the devil, and this overcoming is met with rich promises of reward from Christ.
Scripture teaches that overcoming is not some far off, future achievement that believers hope to reach one day. It is a present reality for those who belong to Christ. The church has already overcome the enemies of God because it has the Spirit of God dwelling within it, the very same Spirit by which Jesus overcame the temptations and power of the devil while He was in the flesh. As it is written, "I write unto you, young men, because ye have overcome the wicked one" and "Ye are of God, little children, and have overcome them: because greater is he that is in you, than he that is in the world." Just as Jesus said of Himself and the Father, "as he is, so are we," this is the truth the church must believe about itself: that it already carries the overcoming nature of Christ.
At the same time, overcoming carries real, ongoing meaning for how a believer lives day to day. To the church at Laodicea, Christ called for repentance from lukewarmness, worldliness, and self-sufficient pride, urging the believers to seek spiritual riches, righteousness, and true spiritual sight rather than resting in outward, worldly prosperity. Overcoming, in that setting, meant turning from complacency back to wholehearted devotion, hearing Christ's voice as He stands and knocks at the door of the heart, and opening to Him so that fellowship and communion can be restored.
Each letter to the seven churches ties overcoming to a specific promise of reward, showing that overcoming is both a present spiritual reality and something with eternal consequence. At Smyrna, those who overcome will not be hurt of the second death. At Pergamos, the overcomer receives hidden manna and a white stone with a new name. At Thyatira, the overcomer is given power over the nations, will rule with a rod of iron, and receives the morning star. At Sardis, those who have not defiled their garments will walk with Christ in white, for they are worthy. At Laodicea, the overcomer is granted to sit with Christ in His throne, just as Christ overcame and now sits with the Father in His throne, meaning the overcomer shares not only in restored fellowship but in royal authority and reign with Him.
So overcoming means living out the victory that Christ has already won and that His Spirit has already placed within the believer, refusing to be conquered by the temptations of the world, the seductions of false doctrine, or the complacency of lukewarm faith, and instead remaining faithful, watchful, and repentant so that the promised rewards, from escaping the second death to reigning with Christ on His throne, become the believer's eternal portion.
The scriptures
I write unto you, fathers, because ye have known him that is from the beginning. I write unto you, young men, because ye have overcome the wicked one. I write unto you, little children, because ye have known the Father.
Ye are of God, little children, and have overcome them: because greater is he that is in you, than he that is in the world.
Philip saith unto him, Lord, shew us the Father, and it sufficeth us. Jesus saith unto him, Have I been so long time with you, and yet hast thou not known me, Philip? he that hath seen me hath seen the Father; and how sayest thou then, Shew us the Father? Believest thou not that I am in the Father, and the Father in me? the words that I speak unto you I speak not of myself: but the Father that dwelleth in me, he doeth the works. Believe me that I am in the Father, and the Father in me: or else believe me for the very works’ sake.
I know thy works, that thou art neither cold nor hot: I would thou wert cold or hot. So then because thou art lukewarm, and neither cold nor hot, I will spue thee out of my mouth. Because thou sayest, I am rich, and increased with goods, and have need of nothing; and knowest not that thou art wretched, and miserable, and poor, and blind, and naked: I counsel thee to buy of me gold tried in the fire, that thou mayest be rich; and white raiment, that thou mayest be clothed, and that the shame of thy nakedness do not appear; and anoint thine eyes with eyesalve, that thou mayest see. As many as I love, I rebuke and chasten: be zealous therefore, and repent. Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me. To him that overcometh will I grant to sit with me in my throne, even as I also overcame, and am set down with my Father in his throne. He that hath an ear, let him hear what the Spirit saith unto the churches.
Because thou hast kept the word of my patience, I also will keep thee from the hour of temptation, which shall come upon all the world, to try them that dwell upon the earth. Behold, I come quickly: hold that fast which thou hast, that no man take thy crown. Him that overcometh will I make a pillar in the temple of my God, and he shall go no more out: and I will write upon him the name of my God, and the name of the city of my God, which is new Jerusalem, which cometh down out of heaven from my God: and I will write upon him my new name. He that hath an ear, let him hear what the Spirit saith unto the churches.
From the books
This answer is drawn from these passages in the Mary Banks Faith Library.