The kingdom of darkness has had its grip on the world for several millennia, but that is all about to come to an end. It has been prophesied that Jesus will return, and when He does, He will bring an end to Satan's dominion over the earth.
When Jesus was describing the days leading up to His return, the first thing He said was to make sure that no one misleads you. Deception will become so prevalent that many will be led astray by false teachers who claim to be believers. He also said that sin would abound and cause people's love to grow cold and that many would stumble.
Knowing how things would go, Jesus exhorts believers to stay alert. We are not to become entangled in the cares of this life, lose our focus, and spiritually fall asleep. But rather we are to remain vigilant, walk in the truth, and encourage others to do so as well.