1 John 2:19
"19 They went out from us, but they did not belong to us. For if they had belonged to us, they would have remained with us. But their departure made it clear that none of them belonged to us. 20 You, however, have an anointing from the Holy One, and all of you know the truth.…"
Just because someone attends church or has attended church for years does not mean they were ever born again.
There are so many who have joined a cultural Christianity in which they follow the rules to fit in. Often rejecting most of God's principles, the ones that are culturally acceptable to ignore.
Most of these cultural Christians do not know their bible, they don't read it, they act embarrassed when the name of Christ comes up but they would identify as Christian.
We do not come to Christ on our own terms, deciding to be a Christian does not save anyone.
Believing on the Lord Jesus Christ to be saved is a decision including the realization that no one can be good enough to earn heaven. Christ paid the penalty of sin, it is His shed blood that covers the sin of the believer. It is His sacrifice that paid it all on that cross. However, there is a condition for the unbeliever, He must trust (believe in Him) Christ to be saved.
Those who have a cultural Christianity to fit into family and to feel safe will not be saved. Their motive is fleshly without a desire to know God or obey Christ.
When we become born again Christ comes to live in us, we love His ways, we fail, confess and go on a little more cleansed.
There are so many who fit into the category of pretenders. They want the safety of the religious system. It gives them a sense of having someone to turn to when things get rough. They want to use God but they don't even really like Him, there is no love for Him and no desire to seek Him unless they are in trouble and want to be bailed out.
These cultural Christians are not born again, they live to self without Christ. Their purpose is safety, personal gratification, friends and self exaltation for any good deeds they do. These deeds are done in the flesh to impress others.
When the name of Christ or His principles are mentioned they become agitated and even angry. Their response to teaching in the word is one of angst toward the one who dared to bring up God's Word. Embarrassment wells up in them when Christ or the Bible is mentioned.
Here is the fate of those who had fleshly good deeds, spiritually and emotionally rejected Christ but pretended to belong to Him:
Matthew 7:21-23
21 “Not everyone who says to Me, ‘Lord, Lord,’ will enter the kingdom of heaven, but he who does the will of My Father who is in heaven will enter.
22 Many will say to Me on that day, ‘Lord, Lord, did we not prophesy in Your name, and in Your name cast out demons, and in Your name perform many miracles?’ 23 And then I will declare to them, ‘I never knew you; depart from Me, you who practice lawlessness.’"
Those who are saved are those whose sins are covered in the blood of Christ. Those who are not saved are those who have rejected Him through self will and aggrandizement.