"'Be on guard! Be alert! You do not know when that time will come. It's like a man going away: He leaves his house and puts his servants in charge, each with their assigned task, and tells the one at the door to keep watch. Therefore keep watch because you do not know when the owner of the house will come back - whether in the evening, or at midnight, or when the rooster crows, or at dawn. If he comes suddenly, do not let him find you sleeping. What I say to you, I say to everyone:"Watch!"'" NIV translation
Jesus reminded His disciples that we are like servants that have been given a job while the master is gone. We are to be about that task until He returns. We will know of His imminent arrival when we see the sign that was given. We all (those in Christ) have a task to do before we meet Jesus. If that task is done before He returns, then, we will go to meet Him. If it is not, then, we should be working at it when He arrives.