One point about Saul, is that even though people might talk about how evil he was, and how wrong he was, and how much he wasn't in God's will, he looked good in front of the people, and that is how the Bible portrays him. Even though Saul also had a distressing spirit, one point as to why we don't jduge by the flesh, and by sight and works, is that David was obviously distressed when he was in the wilderness, and we can read this in the Psalms.

Ezekiel gives a vision regarding God leaving the temple. The cloud of the LORD was in the inner court, and His glory was in the porch area, and then His brightness was in the inner court, and then the sound of wings was in the outer court, having the sound of the voice of the LORD over the waters, and the living creatures lifted up. Beyond this, the word that was used in the Greek in 2 Thessalonians for 'falling away' also means departure. Within this there may be discernment symbolically and literally regarding the church falling away, as with those who overcome are being enraptured, and those who aren't are having the Spirit of God being taken away, just as Jesus spoke about the light in John 12:

John 12:35-36
“A little while longer the light is with you. Walk while you have the light, lest darkness overtake you; he who walks in darkness does not know where he is going. 36 While you have the light, believe in the light, that you may become sons of light.” These things Jesus spoke, and departed, and was hidden from them.

But isn't Jesus called the light of the world, and the light of men, and isn't it impossible that Him being the Light can be taken away? When Jesus predicted His death, He spoke about the hour of darkness, in which He was going to be suffering and overcoming, just as the Psalms also speak about what is called 'the night season.'

Psalm 22:1-2
1 My God, My God, why have You forsaken Me?
Why are You so far from helping Me,
And from the words of My groaning?
2 O My God, I cry in the daytime, but You do not hear;
And in the night season, and am not silent.

Included in this, is the truth about how if we do not wholly seek God, even when things are rough, that we are not going to have Him with us, even if the morning comes. Just as it says:

Psalm 32:6
everyone who is godly shall pray to You
In a time when You may be found

Isaiah 55:6
Seek the LORD while He may be found,
Call upon Him while He is near

So what happens if someone misses their time for the LORD? They are as the parable of the sower, which Jesus gave.

Matthew 13:3-9, 18-23
“Behold, a sower went out to sow. 4 And as he sowed, some seed fell by the wayside; and the birds came and devoured them. 5 Some fell on stony places, where they did not have much earth; and they immediately sprang up because they had no depth of earth. 6 But when the sun was up they were scorched, and because they had no root they withered away. 7 And some fell among thorns, and the thorns sprang up and choked them. 8 But others fell on good ground and yielded a crop: some a hundredfold, some sixty, some thirty. 9 He who has ears to hear, let him hear!”

"hear the parable of the sower: 19 When anyone hears the word of the kingdom, and does not understand it, then the wicked one comes and snatches away what was sown in his heart. This is he who received seed by the wayside. 20 But he who received the seed on stony places, this is he who hears the word and immediately receives it with joy; 21 yet he has no root in himself, but endures only for a while. For when tribulation or persecution arises because of the word, immediately he stumbles. 22 Now he who received seed among the thorns is he who hears the word, and the cares of this world and the deceitfulness of riches choke the word, and he becomes unfruitful. 23 But he who received seed on the good ground is he who hears the word and understands it, who indeed bears fruit and produces: some a hundredfold, some sixty, some thirty.”

This topic of the night season is the main difference between only being called, or coming unto being chosen, and in this, we can also discern that what Jesus said in verse 9 in this chapter and passage is just as He spoke in the letters to the churches, as He also spoke of people overcoming or not. Those who are only called, but do not come unto being chosen, just as Jesus shows in another parable that those who are called but not chosen are unprofitable servants who shall be cast out into outer darkness, are as those He spoke of, in-between these two passages, in which He spoke the parable and then explained it.

Matthew 13:10-17
10 And the disciples came and said to Him, “Why do You speak to them in parables?”
11 He answered and said to them, “Because it has been given to you to know the mysteries of the kingdom of heaven, but to them it has not been given. 12 For whoever has, to him more will be given, and he will have abundance; but whoever does not have, even what he has will be taken away from him. 13 Therefore I speak to them in parables, because seeing they do not see, and hearing they do not hear, nor do they understand. 14 And in them the prophecy of Isaiah is fulfilled, which says:

‘ Hearing you will hear and shall not understand,
And seeing you will see and not perceive;
15 For the hearts of this people have grown dull.
Their ears are hard of hearing,
And their eyes they have closed,
Lest they should see with their eyes and hear with their ears,
Lest they should understand with their hearts and turn,
So that I should heal them.’

16 But blessed are your eyes for they see, and your ears for they hear; 17 for assuredly, I say to you that many prophets and righteous men desired to see what you see, and did not see it, and to hear what you hear, and did not hear it.

And so the dividing line between those who are called and those who are chosen, is found in whether or not someone stays with the LORD in the night season, or whether they just go and do something else. And this is also the foundation for what God speaks about concerning waiting on Him.