There is a Roman god named Janus. We get our month named "January" from this roman figure because he is depicted as someone who has two faces, one looking backward & one looking forward. It's a good image of Advent for during this time we look back to the first coming of Christ when he was born in Bethlehem & we look ahead to the 2nd coming of Christ at the end of time.
Most would prefer to look back at the first coming of Christ. We see him as a gentle, peaceful, even harmless baby in a manger. But then Jesus describes his second coming in the Gospel with a vision that sounds frightening: "There will be signs in the sun, moon & stars. Nations will be in turmoil. People will die of fright in anticipation of what is coming." Why would we want to look for all of that? Jesus was speaking in "apocolyptic" or symbolic language understood in the time of Jesus. It was a powerful way of saying that in the future, God will conquer evil. God will win the battle. God will reign. His Kingdom will come.
Jesus even said that when we see these things happening, we should stand erect with our heads held high for our redemption is near. That's a posture of courage, confidence, hope, expectation and joy. That is what Advent is about, and we should feel just as comfortable looking forward to Christ's coming as we are looking backward to his birth.