I guess you didn't apply "common sense".
John 10:27-28
27 My sheep hear my voice, and I know them, and they follow me:
28 And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand.
“Common sense” without factual support—indeed, there is an abundance of factual support to the contrary—has caused many people to mistakenly believe that this passage supports the doctrine of eternal security even though the parallel passage in Isaiah 43 expressly teaches the opposite!
Isaiah 43: 1. But now thus says the Lord,
he who created you, O Jacob,
he who formed you, O Israel:
Do not fear, for I have redeemed you;
I have called you by name, you are mine.
2. When you pass through the waters, I will be with you;
and through the rivers, they shall not overwhelm you;
when you walk through fire you shall not be burned,
and the flame shall not consume you.
3. For I am the Lord your God,
the Holy One of Israel, your Savior.
I give Egypt as your ransom,
Ethiopia and Seba in exchange for you.
4. Because you are precious in my sight,
and honored, and I love you,
I give people in return for you,
nations in exchange for your life.
5. Do not fear, for I am with you;
I will bring your offspring from the east,
and from the west I will gather you;
6. I will say to the north, "Give them up,"
and to the south, "Do not withhold;
bring my sons from far away
and my daughters from the end of the earth--
7. everyone who is called by my name,
whom I created for my glory,
whom I formed and made."
8. Bring forth the people who are blind, yet have eyes,
who are deaf, yet have ears!
9. Let all the nations gather together,
and let the peoples assemble.
Who among them declared this,
and foretold to us the former things?
Let them bring their witnesses to justify them,
and let them hear and say, "It is true."
10. You are my witnesses, says the Lord,
and my servant whom I have chosen,
so that you may know and believe me
and understand that I am he.
Before me no god was formed,
nor shall there be any after me.
11. I, I am the Lord,
and besides me there is no savior.
12. I declared and saved and proclaimed,
when there was no strange god among you;
and you are my witnesses, says the Lord.
13. I am God, and also henceforth I am He;
there is no one who can deliver from my hand;
I work and who can hinder it?
14. Thus says the Lord,
your Redeemer, the Holy One of Israel:
For your sake I will send to Babylon
and break down all the bars,
and the shouting of the Chaldeans will be turned to lamentation.
15. I am the Lord, your Holy One,
the Creator of Israel, your King.
16. Thus says the Lord,
who makes a way in the sea,
a path in the mighty waters,
17. who brings out chariot and horse,
army and warrior;
they lie down, they cannot rise,
they are extinguished, quenched like a wick:
18. Do not remember the former things,
or consider the things of old.
19. I am about to do a new thing;
now it springs forth, do you not perceive it?
I will make a way in the wilderness
and rivers in the desert.
20. The wild animals will honor me,
the jackals and the ostriches;
for I give water in the wilderness,
rivers in the desert,
to give drink to my chosen people,
21. the people whom I formed for myself
so that they might declare my praise.
22. Yet you did not call upon me, O Jacob;
but you have been weary of me, O Israel!
23. You have not brought me your sheep for burnt offerings,
or honored me with your sacrifices.
I have not burdened you with offerings,
or wearied you with frankincense.
24. You have not bought me sweet cane with money,
or satisfied me with the fat of your sacrifices.
But you have burdened me with your sins;
you have wearied me with your iniquities.
25. I, I am He
who blots out your transgressions for my own sake,
and I will not remember your sins.
26. Accuse me, let us go to trial;
set forth your case, so that you may be proved right.
27. Your first ancestor sinned,
and your interpreters transgressed against me.
28. Therefore I profaned the princes of the sanctuary,
I delivered Jacob to utter destruction,
and Israel to reviling. (NRSV)