One can not lose their salvation, but they can lose their inheritance in being part of the firstfruits of the resurrection, but like the prodigal son that gave up his inheritance for wild living, he will find that he can return because he is still son.One should be careful when they quote scripture...that is not simply present one line of scripture.
Here's the whole verse....from it where do you get the concept you can lose your salvation?
5 But you, be sober in all things, endure hardship, do the work of an evangelist, fulfill your ministry. 6 For I am already being poured out like a drink offering, and the time of my departure is at hand. 7I have fought the good fight, I have finished the race, I have kept the faith. 8 From now on there is laid up for me the crown of righteousness, which the Lord, the righteous Judge, will award to me on that day—and not only to me, but to all who crave His appearing.
The truth here is.. those left behind saints and even former believers are still saved but disqualified to attend the Marriage supper in Heaven. They will be resurrected after the great tribulation. This is where the least in the kingdom of heaven comes from and where the vessels unto dishonor comes from that are still in His House.
Matthew 5:19 Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven.
2 Timothy 2:18 Who concerning the truth have erred, saying that the resurrection is past already; and overthrow the faith of some. 19 Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, let every one that nameth the name of Christ depart from iniquity. 20 But in a great house there are not only vessels of gold and of silver, but also of wood and of earth; and some to honour, and some to dishonour. 21 If a man therefore purge himself from these, he shall be a vessel unto honour, sanctified, and meet for the master's use, and prepared unto every good work.
2 Timothy 2:11 It is a faithful saying: For if we be dead with him, we shall also live with him: 12 If we suffer, we shall also reign with him: if we deny him, he also will deny us: 13 If we believe not, yet he abideth faithful: he cannot deny himself.
That foundation is not going anywhere and neither will that seal of adoption, but He will judge what is on that foundation in that day verse 13.
Ephesians 4:30 And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption.
1 Corinthians 3:10 According to the grace of God which is given unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereupon. 11 For other foundation can no man lay than that is laid, which is Jesus Christ. 12 Now if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble; 13 Every man's work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man's work of what sort it is. 14 If any man's work abide which he hath built thereupon, he shall receive a reward. 15 If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire. 16 Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you? 17 If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which temple ye are.
So there is cause to run that race by faith, looking to the author & finisher of our faith to help us lay aside every weight & sin daily, but not for obtaining salvation, but the high prize of our calling, to be received by Him as that vessel unto honor in His House to His glory.