A man named Demas was a close associate of Paul. Paul even got to call Him a fellow laborer in Christ.
I can imagine the zeal this man carried for the work of the gospel.
But again we later see Paul saying that He left Him because of his love for the world.
The bible says in John 2:15 Do not love the world or anything in the world. If anyone loves the world, love for the Father is not in them.
The two cannot dwell together. Choose today! Whether you will love God or the world. Because whoever you love more overpowers your will over the other.