John 8:31 Then said Jesus to those Jews which believed on him, If ye continue in my word, then are ye my disciples indeed;
Some Jews expressed their faith in Jesus. He tells them that if they really believe that they will continue in His Word. There are many nominal Christians. People who claim to be saved but are not. They join the church. They talk the talk but never really believe. They do what they do from outward conformity but not an inward reality.
Really born again Christians continue in His Word. If He has done a work in you then it is a lasting work. It is not superficial and it will not drop off.
Examine yourself to see if you be in the faith. What is your relationship with the Word? Do you have a hunger and desire to serve God and obey Him?