Zeal is needed to be able to be saved right unto the end. Salvation is a process, not a one-off transaction like so many of us make it out to be. It is a process. The Bible contains more references to 'being saved', rather than that a person 'has been saved':
For the word of the cross is folly to those who are perishing, but to us who are being saved it is the power of God (1 Corinthians 1:18).
For we are the aroma of Christ to God among those who are being saved and among those who are perishing (2 Corinthians 2:15).
and by which you are being saved, if you hold fast to the word I preached to you—unless you believed in vain (1 Corinthians 15:2).
'Being saved' is in the present continuous tense, not in the past perfect tense of being 'already saved'. This indicates that salvation is a process. This has huge implications for those who desire to live a godly life in this world. Such a person must not only humble oneself before God, repent and cry out to God for mercy so that he may be saved by the blood of Jesus Christ, the Son of God, who paid the price for his sins, so that he may be saved from the just wrath of God. He must persevere right to the very end in living a holy and righteous life. This is what Jesus Himself said:
And Jesus answered and said to them: “Take heed that no one deceives you. 5 For many will come in My name, saying, ‘I am the Christ,’ and will deceive many. 6 And you will hear of wars and rumors of wars. See that you are not troubled; for all[a] these things must come to pass, but the end is not yet. 7 For nation will rise against nation, and kingdom against kingdom. And there will be famines, pestilences,[b] and earthquakes in various places. 8 All these are the beginning of sorrows.
9 “Then they will deliver you up to tribulation and kill you, and you will be hated by all nations for My name’s sake. 10 And then many will be offended, will betray one another, and will hate one another. 11 Then many false prophets will rise up and deceive many. 12 And because lawlessness will abound, the love of many will grow cold. 13 But he who endures to the end shall be saved. 14 And this gospel of the kingdom will be preached in all the world as a witness to all the nations, and then the end will come (Matthew 24:4-14).
In Matthew 10:21-22:
“Now brother will deliver up brother to death, and a father his child; and children will rise up against parents and cause them to be put to death. 22 And you will be hated by all for My name’s sake. But he who endures to the end will be saved.
In order to persevere to the end, one must fully submit oneself to the Lord God, and His alone, fully trusting in Him and Him alone, and in nothing else. It is a lack of faith, that is belief in God in the sense of trusting in Him that leads people to fall away. It is because of this tendency that all of us are susceptible to that we all need constant exhortation to remain faithful to God. Hebrews 3:12-15 makes this clear:
Do not harden your hearts as in the rebellion.”
Therefore we also, since we are surrounded by so great a cloud of witnesses, let us lay aside every weight, and the sin which so easily ensnares us, and let us run with endurance the race that is set before us, 2 looking unto Jesus, the author and finisher of our faith, who for the joy that was set before Him endured the cross, despising the shame, and has sat down at the right hand of the throne of God (Hebrews 12:1-2).