Jesus said: I know thy works, that thou art neither cold or hot; I would thou wert cold or hot.

16 So then because thou art lukewarm, and neither cold nor hot, I will spue thee out of my mouth.

He is talking bout churches

He did not say they were not saved!

The waters of the nearby Lycus River were muddy and undrinkable, and the waters flowing by aqueduct from hot springs 5 miles (8 km) away were lukewarm when they reached Laodicea. Likewise, Jesus found his church's tepid indifference repugnant. Cold and hot water represent something positive, for cold water refreshes in the heat, and hot water is a tonic when one is chilly.

In 17-20 the case is layed out Hermenueticly, the spiritually blind, bankrupt, naked Laodiceans obviously had no resources to buy from Jesus gold or garments or salveIsa. 55:1–4). for their eyes. They could “purchase” these necessities only by his grace, as the Lord had once invited thirsty spiritual paupers to “buy wine and milk without money” Like a loving father, Christ will reprove those whom he loves (cf. Prov. 3:12), calling them to repent before he intervenes in judgment. I stand at the door and knock, not as a homeless transient seeking shelter but as the master of the house, expecting alert servants to respond immediately to his signal and welcome his entrance

How do you account for the parable of the sower of seeds and those who fall away when the going gets tough?

Hermenutics dicates that scripture be used to interprit scripture.

Lets look at the entire passage so we see the context.

Matthew 13

 1 That same day Jesus went out of the house and sat beside the sea. 2 And great crowds gathered about him, so that he got into a boat and sat down. And the whole crowd stood on the beach. 3 And he told them many things in parables, saying: A sower went out to sow. 4 And as he sowed, some seeds fell along the path, and the birds came and devoured them. 5 Other seeds fell on rocky ground, where they did not have much soil, and immediately they sprang up, since they had no depth of soil, 6 but when the sun rose they were scorched. And since they had no root, they withered away. 7 Other seeds fell among thorns, and the thorns grew up and choked them. 8 Other seeds fell on good soil and produced grain, some a hundredfold, some sixty, some thirty. 9 He who has ears, let him hear.

10 Then the disciples came and said to him, Why do you speak to them in parables? 11 And he answered them, To you it has been given to know the secrets of the kingdom of heaven, but to them it has not been given.

What?!?!?!?!?

12 For to the one who has, more will be given, and he will have an abundance, but from the one who has not, even what he has will be taken away. 13 This is why I speak to them in parables, because seeing they do not see, and hearing they do not hear, nor do they understand. 14 Indeed, in their case the prophecy of Isaiah is fulfilled that says:
“You will indeed hear but never understand,
and you will indeed see but never perceive.
15 For this people's heart has grown dull,
and with their ears they can barely hear,
and their eyes they have closed,
lest they should see with their eyes
and hear with their ears
and understand with their heart
and turn, and I would heal them.

(From Isaiah 6:10 Make the heart of this people dull,
and their ears heavy,
and blind their eyes;
lest they see with their eyes,
and hear with their ears,
and understand with their hearts,
and turn and be healed.)

So God Made them purposely to be people who could not hear nor see

16 But blessed are your eyes, for they see, and your ears, for they hear. 17 Truly, I say to you, many prophets and righteous people longed to see what you see, and did not see it, and to hear what you hear, and did not hear it.

18 “Hear then the parable of the sower: 19 When anyone hears the word of the kingdom and does not understand it, the evil one comes and snatches away what has been sown in his heart. This is what was sown along the path. 20 As for what was sown on rocky ground, this is the one who hears the word and immediately receives it with joy, 21 yet he has no root in himself, but endures for a while, and when tribulation or persecution arises on account of the word, immediately he falls away. 22 As for what was sown among thorns, this is the one who hears the word, but the cares of the world and the deceitfulness of riches choke the word, and it proves unfruitful. 23 As for what was sown on good soil, this is the one who hears the word and understands it.(look back in verse 13) He indeed bears fruit and yields, in one case a hundredfold, in another sixty, and in another thirty.

This is the only person that was part of the flock that Jesus spoke of in john 6

What about all the other parables where Jesus warns people about falling away?

There are none!

How can you just take the part of the Bible that suits your way of thinking and ignore the rest of the Bible?

I have shown that is not the case. That if you would have just read a few more verses it would have been defined.

Hermenutics dicates that scripture be used to interprit scripture.