One who does not see eternal life in the passage did not read it, cannot read it, will not read it, or is spiritually blinded and cannot spiritually discern it. Read it slowly, verse by verse. Pretend it was not posted by a Catholic if that helps. It is more important that one not publicly add to, or take away from, the words in the prophecy.
Rev 22:8 Now I, John, am the one who heard and saw these things. When I heard and saw, I fell down to worship before the feet of the angel who had shown me these things. He said to me, "See you don't do it! I am a fellow bondservant with you and with your brothers, the prophets, and with those who keep the words of this book. Worship God." [The one to whom John fell down was a servant, an Angel. So this one is IN HEAVEN; if you will recall, the twenty four elders seen after Rev 4:1 concluded and the scene shifted to Heaven. Let's read further ...]He said to me, "Don't seal up the words of the prophecy of this book, for the time is at hand. He who acts unjustly, let him act unjustly still. He who is filthy, let him be filthy still. He who is righteous, let him do righteousness still. He who is holy, let him be holy still." [This tells readers that the prophecy is given in John's day, but it is a book/prophecy aimed at the ages to come from that day onward. Here are two groups, those filthy and those righteous, and we know that righteousness is the result of God's Grace by believing God and it is counted for him righteousness.] 12 "Behold, I come quickly. My reward is with me, to repay to each man according to his work. I am the Alpha and the Omega, the First and the Last, the Beginning and the End. [Even a catholic should get the gist of that identity! The quotation continues ...]
14 Blessed are those who do his commandments, that they may have the right to the tree of life, and may enter in by the gates into the city. Outside are the dogs, the sorcerers, the sexually immoral, the murderers, the idolaters, and everyone who loves and practices falsehood. [Refer immediately back to the scene where the Tree of Life is shown as opened to those alive in bodies at the end of the Tribulation. We have gotten to the parts that require real knowledge of the previous passages, because there are clear segmentations from Chapter four right through to the end of the Tribulation written of. The perspective is from Heaven, as John has been 'lifted up through the door he saw open in Rev4:1. From here on it is important to see to whom the passages previously given referred to, as in the earth dwellers who were left on Earth AFTER Jesus accomplished what He promised tot he Church in Philadelphia, prefiguring the born from above who remain active in His Grace, being raised up in the Way that they should go by the real Presence of God's Spirit in them. That is a hard saying for catholics, since they are taught they must strive to obtain eternal life, but God tells us in The Word that He immediately seals those born from above, by placing His Holy Spirit in them, as illustrated for us at the Day of Pentecost and in the House of Cornelius, with the Holy Spirit going into the believers immediately upon broken and contrite hearts exhibited to God's perspective. The quote continues ...]
16 I, Jesus, have sent my angel to testify these things to you for the assemblies. I am the root and the offspring of David; the Bright and Morning Star." 17 The Spirit and the bride say, "Come!" He who hears, let him say, "Come!" He who is thirsty, let him come. He who desires, let him take the water of life freely.
18 I testify to everyone who hears the words of the prophecy of this book, if anyone adds to them, may God add to him the plagues which are written in this book. If anyone takes away from the words of the book of this prophecy, may God take away his part from the tree of life, and out of the holy city, which are written in this book.
20 He who testifies these things says, "Yes, I come quickly." Amen! Yes, come, Lord Jesus.
21 The grace of the Lord Jesus Christ be with all the saints. Amen.
To fully comprehend what JESUS is telling you in this conclusion, it is important to know there is more than one group to whom the Revelation of John refers. If you do not believe in the Rapture (as most catechized catholics do not believe there is a Rapture of the Bride coming), it will be hard to accept the following, but it is sound teaching.
Look at verse 17 and see that 'The Spirit and The Bride say come'. This is a huge clue that 'The Bride of Christ' is already secure in Heaven with Jesus, so the references to whom the Spirit and The Bride say come must be getting an invitation to something important!
The Bride (The Body of Christ, The Believers saved by His Grace as they Trusted only in His Grace not their filthy works) is already enjoying eternal life, so this passage is not directed to the Bride of Christ but to others. These others are being instructed that REWARDS are in the possession and purview of The Lord Jesus, not some earthy organization such as the Methodist or Baptists or Catholicism.
Verse 19: "If anyone takes away from the words of the book of this prophecy, may God take away his part from the tree of life, and out of the holy city, which are written in this book." To fully understand what Jesus is saying, you need to reference back to when and by what scene The Holy City' is referenced, and to whom and what group already has residence in The Holy City'. And yet again to a different group referred to earlier in the Revelation, who is given access to the Tree of Life, to continue living in a 4D body, on Earth, AFTER the Great Tribulation, into the millennium. The reference to the tree of life refers readers back to a previous passage dealing with those who will come through the Great Tribulation alive and enter into the millennial Kingdom and eat from the tree of life to remain physically 4D alive on earth. The Holy City is built after the Bride is taken back to 'the Father's House', and refers to a city which will be hallmark during the millennial reign of Christ and His Bride. This Holy City is shown descending to the Earth.
We see that Jesus is referring to the alive on the earth, from that day through to the present day: "He who acts unjustly, let him act unjustly still. He who is filthy, let him be filthy still. He who is righteous, let him do righteousness still." All those are still in their bodies.
Then we see that Jesus cites those who are right then the day of the prophecy, Holy, such as those believers who have died in Christ, the ones God will bring with Him for the Rapture, as revealed by Paul in 1 Thess 4:13-18; I Cor 15:521-53; 2 Thess 2) "He who is holy, let him be holy still."
So the passage ends with a warning not to add or take away from the Prophecy. The passage before the warning focus upon those who ARE NOT THE BRIDE of CHRIST, for these the passage refers to Jesus bringing REWARDS for those (not the Bride, the rewards have already been meted at The Bema Seat in Heaven for the Bride) who come. Jesus has His rewards for the earth dwellers sorted during the Tribulation, and The Spirit and The Bride speak to these and say come, so the Bride is already fitted, rewarded, and put to assignment.
In the Revelation, John is shown scenes from the future, and the time frame shifts back and forth and the scene shifts back and forth from Heaven to earth and back to Heaven, as tiems and events are revealed. From Rev 4:1 through to the notneenth chapter, the Chruch is not referred to. BUT the Bride is referred to, in Heaven, then coming again with The King to the Earth at the end of the Great Tribulation. Now, have a gay old time arguing with that!
IF a catholic believes they are already Saved, possessing eternal life in them, then the passage you cited is not aimed at them regarding eternal life because Jesus refers to those to whom The Bride and The Spirit say 'come' to receive the rewards Jesus brings with Him at the end of the Great Tribulation. IF, on the other hand, a catholic believes they must strive to obtain eternal life, they are in danger of getting the wrong kind of rewards Jesus will bring with Hima nd His Bride, to the separating of the goats and sheep identified through the Tribulation.