Seizing the Kingdom of Heaven by Force

An old, dear friend and the best Bible teacher I've ever known taught that the key to understanding the Gospel was the passage in Matthew 11:12 :

^" From the days of John the Baptist until now the kingdom of heaven suffers violence, and violent men take it by force."

But I always struggled to try to understand what my friend meant until I saw the film, The Polar Express.  Billy explained it better than any theologian could have: