John 6:66 From that time many of his disciples went back, and walked no more with him.

Sadly following Jesus does not guarantee you have saving faith in Christ. These were disciples, they followed Jesus, but then they stopped. If their faith had been a saving faith, their faith would have been an abiding faith.

John 15:4 Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me.

The vine is the extension of the root system which bring life to the branches and is responsible for ensuring fruit. Without a connection to the root system, there is no life.

Ephesians 3:16-19  That he would grant you, according to the riches of his glory, to be strengthened with might by his Spirit in the inner man; That Christ may dwell in your hearts by faith; that ye, being rooted and grounded in love, May be able to comprehend with all saints what is the breadth, and length, and depth, and height; And to know the love of Christ, which passeth knowledge, that ye might be filled with all the fulness of God.

Joy for a moment does not indicate life is rooted and grounded in God’s love.

Matthew 13:20-21  But he that received the seed into stony places, the same is he that heareth the word, and anon with joy receiveth it; Yet hath he not root in himself, but dureth for a while: for when tribulation or persecution ariseth because of the word, by and by he is offended.

Nothing is more painful to a parent or family member as to see the joy of salvation last for only a season. Our hope is that it is true salvation but we deceive ourselves if we leave them to rest in a faith that does not save.