1 John 2:19 They went out from us, but they were not of us; for if they had been of us, they would have continued with us; but they went out that they might be made manifest, that none of them were of us.

My memory of this verse is relatively new.
About 5 years ago a friend was searching for an answer to how someone could claim salvation, perhaps serve in the church for years, and then completely turn their back on God.
I tried to come up with scripture but it did not help answer the question.
My friend began fasting and eventually found today’s scripture.
It is a difficult matter to understand.
I know a few people angry at God because something did not go their way.
Perhaps it was the death of a child or they believed in a healing that did not manifest.
I have also known those stepping forward for salvation and baptism.
They attend church and help where and when they can.
Then they quit with no explanation.
Personally, for me, a great part of serving God is getting up in the morning and putting one foot in front of the other.
Anyone can throw up their hands and quit.
God never promised the journey would be easy.
Taking up the cross and following Jesus is often difficult but rewarding.
Of course, only God knows the heart and writes or blots out names in the Book of Life.
It is not for us to judge whether someone is truly saved or not of us.
It is up to us to pray for those struggling with temptations that keep them from the Lord’s service.