Question:
What if somebody accepts Christ and then later leaves Him and leads a life not pleasing to Him?

Answer:
Those that are the Lord’s sometimes might stray, but they are still saved for the Lord keeps them. When praying to the Father Jesus said: “While I was with them in the world, I kept them in Thy name: those that thou gavest Me I have kept, and none of them is lost, but the son of perdition [Judas]; that the scripture might be fulfilled” (John 17:12).

The Lord seeks to restore His people to happy fellowship with Himself, and God disciplines such, not as a judge but as a Father. “For the Lord disciplines the one He loves, and chastises every son whom he receives” (Hebrews 12:6).