Fall from grace, once saved always saved; both phrases say the same thing. This basic idea is that we are saved when we do something. The something is determined by which denominational church you happen to ask. Then from that point on, you are saved and you cannot fall out of the state of being saved. The reason you cannot fall is because of God's Grace. If you think it takes works beyond this point of being saved, than it would be by your works and not by God's grace that saves you. The following is a verse that backs the general theory:
 

Romans 11:6 And if by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then is it no more grace: otherwise work is no more work.
 

According to this verse they might be onto something. Where their thinking falls short is that grace comes through faith.
 

Romans 3:27 Where is boasting then? It is excluded. By what law? of works? Nay: but by the law of faith.28 Therefore we conclude that a man is justified by faith without the deeds of the law.
 

Romans 9:32 Wherefore? Because they sought it not by faith, but as it were by the works of the law. For they stumbled at that stumbling stone; 
 

Galatians 2:16 Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified.
 

Ephesians 2:8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: 9 Not of works, lest any man should boast. 10 For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.
 

So if we're saved by grace because of our faith, then work is still not necessary, right, WRONG. Here's where our works are needed. By works we show our faith. If we're not doing good works, our faith is mere hear say.
 

James 2:14 What doth it profit, my brethren, though a man say he hath faith, and have not works? can faith save him?
 

James 2:17 Even so faith, if it hath not works, is dead, being alone.
 

James 2:18 Yea, a man may say, Thou hast faith, and I have works: show me thy faith without thy works, and I will show thee my faith by my works.
 

James 2:20 But wilt thou know, O vain man, that faith without works is dead?
 

James 2:21 Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar?
 

James 2:22 Seest thou how faith wrought with his works, and by works was faith made perfect?
 

James 2:24 Ye see then how that by works a man is justified, and not by faith only.
 

James 2:25 Likewise also was not Rahab the harlot justified by works, when she had received the messengers, and had sent them out another way?
 

James 2:26 For as the body without the spirit is dead, so faith without works is dead also
 

The misconception is if you believe your works are what saves you, than your wrong, but works are still necessary. You can not save yourself. You do good works because it is a commandment and it shows you have faith. To not do "good works" is a sin. Works will not save you, but no works or bad works, will condemn you.
 

Matthew 16:27 For the Son of man shall come in the glory of his Father with his angels; and then he shall reward every man according to his works.
 

1 Corinthians 3:13 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. 
 

1 Corinthians 3:14 If any man’s work abide which he hath built thereupon, he shall receive a reward. 
 

1 Corinthians 15:58Therefore, my beloved brethren, be ye steadfast, unmovable, always abounding in the work of the Lord, forasmuch as ye know that your labor is not in vain in the Lord. 
 

2 Corinthians11:13 For such are false apostles, deceitful workers, transforming themselves into the apostles of Christ. 14 And no marvel; for Satan himself is transformed into an angel of light. 15 Therefore it is no great thing if his ministers also be transformed as the ministers of righteousness; whose end shall be according to their works 
 

1 Thessalonians 4:11 And that ye study to be quiet, and to do your own business, and to work with your own hands, as we commanded you; 
 

2 Timothy 4:5 But watch thou in all things, endure afflictions, do the work of an evangelist, make full proof of thy ministry. 
 

Titus 1:16 They profess that they know God; but in works they deny him, being abominable, and disobedient, and unto every good work reprobate. 
 

James 1:25But whoso looketh into the perfect law of liberty, and continueth therein, he being not a forgetful hearer, but a doer of the work, this man shall be blessed in his deed. 
 

Revelation 22:12 And, behold, I come quickly; and my reward is with me, to give every man according as his work shall be.
 

So let's put this together. We are saved by God's grace; grace is freely given to those who have faith and our works show faith. So what happens if we stop our works? I think the answer to that is we would fall from grace. But there are no scriptures to back this theoryare there? 
 

Matthew 13:22 He also that received seed among the thorns is he that heareth the word; and the care of this world, and the deceitfulness of riches, choke the word, and he becomes unfruitful. 
 
 

1Corinthians 10:12 Wherefore let him that thinketh he standeth take heed lest he fall. 
 

1 Tim. 4:1 Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils; 2 Speaking lies in hypocrisy; having their conscience seared with a hot iron; 
 

Heb. 2: 1 Therefore we ought to give the more earnest heed to the things which we have heard, lest at any time we should let them slip. 
 

Heb. 3: 12 Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God. 
 

Heb. 4: 1 Let us therefore fear, lest, a promise being left us of entering into his rest, any of you should seem to come short of it. 
 

Heb. 4: 11 Let us labor therefore to enter into that rest, lest any man fall after the same example of unbelief. 
 

Heb. 12: 15 Looking diligently lest any man fail of the grace of God; lest any root of bitterness springing up trouble you, and thereby many be defiled; 
 

2 Peter 3: 17 Ye therefore, beloved, seeing ye know these things before, beware lest ye also, being led away with the error of the wicked, fall from your own steadfastness.

Courtesy of http://www.rmcoc.com/faq/faq.htm