The Apostle Paul and Peter delve nicely into this subject matter, as it's extremely important to the maintenance our Salvation. Yes, Salvation must be maintained. A negligent and slothful believer will surely fall from Grace and lose their Salvation. I am not saying that it cannot be recaptured, for our God is merciful. King David, as an example, was able to recapture his Salvation, but how many never get it back? Whatever spiritual state you die in, determines your eternity in Heaven or Hell. Will you die in Grace or fallen from Grace? Death can seize at any time, so we must be vigilant to maintain our spiritual garments so as not to defile them. Consistent prayer, fasting and living in the Word of God will keep a believer's garments white as snow.
Galatians 5
16 This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.
17 For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.
24 And they that are Christ's have crucified the flesh with the affections and lusts.
25 If we live in the Spirit, let us also walk in the Spirit.
Romans 8
1 There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.
13 For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live.
1 Peter 2
11 Dearly beloved, I beseech you as strangers and pilgrims, abstain from fleshly lusts, which war against the soul;
1 Peter 4
1 Forasmuch then as Christ hath suffered for us in the flesh, arm yourselves likewise with the same mind: for he that hath suffered in the flesh hath ceased from sin;
2 That he no longer should live the rest of his time in the flesh to the lusts of men, but to the will of God.
3 For the time past of our life may suffice us to have wrought the will of the Gentiles, when we walked in lasciviousness, lusts, excess of wine, revellings, banquetings, and abominable idolatries:
4 Wherein they think it strange that ye run not with them to the same excess of riot, speaking evil of you:
5 Who shall give account to him that is ready to judge the quick and the dead.