Verse: Mark 13:1-37

When one of the disciples show Jesus the enormity of the buildings and stones around them, Jesus replies with "Not one stone here will be left on another; every one will be thrown down.", reminding them that everything that has to do with Man is temporary, God is Forever. Jesus goes on to warn them that the world will, in time, seem to go mad. "Nation will rise against nation, and kingdom against kingdom. There will be earthquakes in various places, and famines. These are the beginning of birth pains.
You must be on your guard."
Jesus tells them all of this so that they (and their future counterparts) are prepared. They know what to believe and not to believe.
It is important that we prepare ourselves similarly, and know what is false.
Jesus then warns us to be watchful, to always be prepared for the coming of the Lord. When He comes, we must be prepared, both in Mind, and in Soul. If we are prepared, then leaving Earth will not be difficult for us.