We have reduced the gospel into hearer-friendly material, which introduces you to 3 things.

1) The goodness of God in loving you for whatever you are.
2) Promising you eternal life.
3) Showering you with gifts and blessings.

Everybody loves a God like that. That is why everybody celebrates Christmas, because it sells the idea of an old fat dude, who drops in and gives you gifts for no good reason and assures you you're being a good boy/ girl, keep up your good work.
Of course you would welcome such a god.

If you believe, you're only believing in the goodness and abundant gifts this god has to offer and you're intaking a god that prospers you, agrees with whatever you are doing no matter how immoral it is, and leaves you alone to enjoy yourself at most of the time.

That is not the God of scripture or Yahweh, but a man-made consultant you've crafted to serve your own sinful desires. This god you've made serves your own human whims and desires instead of you serving him.

This is what is the gospel is:

1) Men are so wicked and fallen that we have no hope, no control over ourselves.
2) God's wrath is upon us because of our sin.
3) He had mercy on us and sacrificed his Son to redeem us which we could not have done for ourselves previously.

The gospel is unsavoury and offensive. It is like a slap to your face.
If you accept it casually, you have not understood it.

We have diluted the meaning of believing in Christ.
Scripture indeed does say that you are to believe in Christ, and that is the route to salvation.
You firstly would have believed in all the nice things about Jesus, and are looking for more promise of goodness.

You are like the five thousand whom Jesus fed and are looking for him. You're looking to benefit more, not because you believe in Jesus' divine power.

John 6: 26
Jesus answered, "I tell you the truth, you are looking for me, not because you saw miraculous signs but because you ate the loaves and had your fill."

The Bible says to believe and confess that Jesus is the Christ and Son of God. And so you think your frivolous verbal declarations are enough and you believe in him would mean that you have faith and you are saved.

Do you really know what it means to believe? It is not just to acknowledge and accept what is said. It is to devote and to hope in Jesus and to give up your life for him.
In those times, if you were to confess Christ is Lord, you would be killed.

To believe is to throw yourself, your hopes and your confidence onto Him that He is your sustenance, He is your provider and He is your God.

Is this the depth of your belief?
Or do you treat 'believing' like a vaccination and an insurance where you've bought a unit in heaven?
Can you be sure this is the depth of your belief?

Peter disowned Jesus thrice, even though he declared Jesus to be the 'Holy One of God' earlier.
Are you better than him?

A common blasphemous belief is that once you believe, you're a Christian and you're automatically guaranteed a place in heaven.
Who told you that? Firstly, is your belief and faith of God and in God?
Then, are you behaving like a Christian?

Matthew 7: 13
"Enter through the narrow gate. For wide is the gate and broad is the road that leads to destruction, and many enter through it. But small is the gate and narrow the road that leads to life, and only a few find it."

In addition to the gate being small, the path that leads to the gate is narrow and many will fall off. Do you think Jesus was lying when he said that only a few will find it?

Beware. Firstly, your belief could be false and misplaced. You do not believe in the unbelievable gospel of Jesus Christ because it makes sense to you or it appeals to you.
God has mercy on you and gives you the gift of faith. Otherwise you would never swallow the gospel's message.

If you have been marked out by God, he will have changed you and put in you a God-loving and seeking heart that will continously walk after him. God will give you the ability you never had to turn away from and stop sinning like you were before.

If such a change has not taken place in you, you have not been saved. Nobody has a heart that seeks and wants God. God gives you such a heart and changes you.

When God saves you, you will know that you are different and you will be born again, having a new heart and new wants that are of God. When he takes you as one of his, he will keep you and discipline you and teach you.

If you continue to enjoy living like you once did, still remaining preoccupied about worldly concerns of pleasure and fun, you can be sure you have not been touched by God.

You profess to be Christians, yet you do not read God's word. If you do read, you're reading it to gratify yourselves and to use Scripture to justify your carnal desires. Read scripture and read it carefully and pray that the God of Abraham, Issac and Jacob reveals himself to you.

Not everyone has known God. Your human efforts to try and find and reach God is futile and misguided. You would not be able to get to God no matter how hard you try. That is why there is a need for Jesus. Even then, you remain blocked, your hearts are still stone and you will not be able to get to God.

John 6:44
"No one can come to me unless the Father who sent me draws him, and I will raise him up at the last day."

After Jesus said this, many of the disciples who believed in Jesus rejected his teachings and deserted him.

A lot of us are the disciples who do not know Jesus yet and we would be driven away if we know the entirety of the gospel, unless God keeps us.

John 6: 63
"The Spirit gives life; the flesh counts for nothing. The words I have spoken to you are spirit and they have life. Yet there are some of you who do not believe." For Jesus had known from the beginning which of them did not believe and who would betray him. He went on to say, "This is why I told you that no one can come to me unless the Father has enabled him."

Jesus knows who of us believe because he has already marked us out.
Do not presume yourself to be included in his flock of sheep, but rather examine yourselves.

Jesus' sheep hear his voice and follow after him. If you do not hear and you're not following after him, you are not his sheep.

John 10: 14
"I am the good shepherd; I know my sheep and my sheep know me-just as the Father knows me and I know the Father-and I lay down my life for the sheep."

John 10: 24-
The Jews gathered around him, saying, "How long will you keep us in suspense? If you are the Christ, tell us plainly."
Jesus answered, "I did tell you, but you do not believe. The miracles I do in my Father's name speak for me, but you do not believe because you are not my sheep. My sheep listen to my voice and they follow me. I give them eternal life, and they shall never perish; no one can snatch them out of my hand. My Father, who has given them to me, is greater than all; no one can snatch them out of my Father's hand. I and the Father are one."

Jesus' sheep are those whom he has enabled to believe in him, and they will follow unwaveringly after him and not fall away. He guarantees that no one will be able to snatch them away from him, the shepherd and that their salvation is assured.

Jesus' elect is not a broad net. It is a small pen which is reserved for those God has designated.
Rather, you should be very afraid and concerned if you are one of Jesus' sheep.

If you do not understand the above, then I will have this to say:

John 8: 47
He who belongs to God hears what God says. The reason you do not hear is that you do not belong to God.

Instead of presuming you are one of Jesus' sheep, pray rather that you will receive his mercy and be included in his flock.