The Trial of a Saving Interest in Christ

"Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new."
In this verse Paul delineates the true Christian.
1 The wonderful change: "a new creature."
2 Explaining the change: "old things are passed away."
3 The rarity of this experience: "if any man..."
How can I be sure that I am a new creature in Christ? Do you enjoy the Word of God, and the worship of God? Do you understand the difference between the old creature and the new creature in Christ, the old life and the new life?
Application 1. To be without regeneration is a most miserable condition. 2. To be a new creature in Christ is a glorious privilege. 3. Since the new creation is a work of God do not despair about unconverted loved ones. 4. How small is the number of new creatures. 5. Since none be in Christ but new creatures, let no-one try to make Christianity something different.