What happens with people who fall away beyond repentance? Salvation is no longer offered to them. This is why Christ tells us:

John 12:35
Walk while you have the light

When people walk while they have the light, they are sowing to the light, in God's Promises and His oneness. One of the biggest reasons why God said:

Isaiah 50:11
all you who kindle a fire,
Who encircle yourselves with sparks:
Walk in the light of your fire and in the sparks you have kindled—
This you shall have from My hand:
You shall lie down in torment.

is because when people are kindling fires that they themselves put out, and yet at the same time are also judging the reason that they put them out, as to being because of a lack of fruit from the LORD, they are judging themselves, just as they shouldn't have even began, if they weren't wholly going to finish, and thus Jesus says:

Luke 14:28-32
which of you, intending to build a tower, does not sit down first and count the cost, whether he has enough to finish it— 29 lest, after he has laid the foundation, and is not able to finish, all who see it begin to mock him, 30 saying, ‘This man began to build and was not able to finish’? 31 Or what king, going to make war against another king, does not sit down first and consider whether he is able with ten thousand to meet him who comes against him with twenty thousand? 32 Or else, while the other is still a great way off, he sends a delegation and asks conditions of peace.

And the context of this verse is centered around the cross, and so when Jesus spoke this, He was speaking it regarding following Him wholly, even when we might have to lose some of the things that are prosperous according to the rule of the world. That is why it says:

Luke 14:33
whoever of you does not forsake all that he has cannot be My disciple

What is the prosperity of the world? It is the things that the people mentioned in the be-attitudes do not choose over God's oneness and His Promises, as with the people mentioned in Hebrews 11. The very truth about how the Spirit is our Rock and foundation shows how it is possible to seem to be sturdy, and yet only be built on the sandy foundation which is accepted in the world, because the world has been given to remain for a short while. And this is why and how the Bible speaks about people who left the safety and peace that they had in the world, and poured themselves out for the Promises and oneness of God. There is no 'testing of the water' as far as following the LORD. The Bible clearly says and shows that if we are not for God we are against Him. And therefore attempting to only put our toe in the water, concerning following God, is the very meaning of Luke 14:28-32. And this is what is addressed in Isaiah 50:11. That kind of doubleness may seem to be zealous and open for God, but it encircles itself with reasons as to why it doesn't have to follow God, if things require perseverance and endurance, such as not possessing the prosperous things of the world, but eagerly willingly laying down what the world and the friends of it would call good, even through testing, fire, water, affliction, and suffering. We can surely know that there is a difference between faith and hope, and in this we may discern the oneness of God, as hope concerns the future and faith concerns the present. It is those who only honor God with the lips, as Isaiah and Jesus spoke about, who attempt to only be open and zealous for the LORD regarding hope, because they are merely setting themselves up in doubleness, as doing so may allow them to prosper in the world temporarily, but then seek God only according to their own view of pouring themselves out. And this is what was happening in Psalm 78 concerning the Israelites:

Psalm 78:34-42
When He slew them, then they sought Him;
And they returned and sought earnestly for God.
35 Then they remembered that God was their rock,
And the Most High God their Redeemer.
36 Nevertheless they flattered Him with their mouth,
And they lied to Him with their tongue;
37 For their heart was not steadfast with Him,
Nor were they faithful in His covenant.
38 But He, being full of compassion, forgave their iniquity,
And did not destroy them.
Yes, many a time He turned His anger away,
And did not stir up all His wrath;
39 For He remembered that they were but flesh,
A breath that passes away and does not come again.

40 How often they provoked Him in the wilderness,
And grieved Him in the desert!
41 Yes, again and again they tempted God,
And limited the Holy One of Israel.
42 They did not remember His power

Verse 42 gives a very direct word concerning the difference between being faithful in God, and being double unto Him. Knowing His power is crucial in following Him. Through not trusting Him and through having doubt and unbelief regarding His power, His power came against the Israelites. But the word of Christ says that all things are possible for those who believe, and that what is impossible with men is possible with God. Through those words from Christ, we may know that when our reasons for the decisions that we make pertain to what we think is possible and impossible, that we are ourselves with knowledge and beginning to judge. And this is why God says that it is a fearful thing to fall into the hands of God, because our judgments then begin to be willful. It is because of this, that falling away beyond repentance through willfully sinning, while having the knowledge of the truth, that the unpardonable sin concerns the actions that we have which are directed away from the LORD. And this is why it is so important to prepare the way, because when we are penitent, and understand that we can repent and believe in God even when we are sinning, we can still be turned towards Him, and sowing unto Him. That is the oil that the five virgins brought enough of. And that gives us to be able to know that we are not ourselves sinning, but that we are taken captive as our feet are dirty, and as our outward person is perishing. And thus since the new birth gives for the inward person to be incorruptible, perfect, and sinless, so is it the foundation that is built on the Rock, which is fully reconciled to the LORD, and without guile, concerning God’s judgments in our oneness deciding what the will of God is, and what He can do. And so God's severity is found both in how we can judge against God's will, and also claim something is His will when it isn't. And this is the largest part which has to do with the sandy foundation regarding lukewarmness, being double, and following peace and safety that is not in His oneness. And what is the greatest motivation in this? Complacency. Complacency is that foundation I was speaking of, in which a person attempts to only be concerned with God according to hope, as it is in the future, but then also attempts to follow the dictates of their own heart and mind, regarding faith and what is in the present, just as some only honor Him with their lips.

God said both that the blind will remain blind, and the deaf will remain deaf, concerning those who only honor Him with the lips, and that they will have that from His hand, lest He turn to them and heal them, when they are not actually continually led by Him. And this is one major reason that only attempting to follow prosperity, and peace and safety can not enter in.

David was surely covered with many things, as he was in the wilderness. Things that probably made him seem crazy, just as the Psalms show, and just as the others were judging him. So was it David who was not right with the LORD that whole time, as God would have given him victory earlier if he had been? No. God waited until the fullness of perdition and condemnation came unto those who were with Saul, though they might have believed that it was David who was not right with God.