My sheep hear my voice, and I know them, and they follow me. I give them eternal life, and they will never perish, and no one will snatch them out of my hand. My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father’s hand. -John 10:27–30.
Jesus describes a true believer: someone who hears, believes, and then follows, our Lord Jesus. Their life gives evidence of a true conversion experience.
These people (those who have embraced and now follow, Christ) have received eternal life immediately. We are guaranteed Heaven because it is given to us as a gift. This gift humbles us, encourages us, and motivates us to deeper service to the King.
The Bible tells us to "examine ourselves to see if we are in the faith." Do you see the heart of Jesus growing in you? If you don't, ask God to open the eyes of your heart so you can see and embrace and follow Him. If you see that you are being made new by our Lord Jesus . . . know this: Once you are in the family He will never let anyone or anything take you from His hand. Thanks be to God.