You also must be prepared, for at an hour you do not expect, the Son of Man will come.
So often we read this passage merely as a warning looking toward the judgement that will come.
If we read it however in the full context of the gospel, the good news of Jesus Christ, the coming of the Son of Man is not something to be feared but something to be hoped for.
There is also a more immediate reading of the passage. We should keep our eyes open and be prepared to see the action of Christ in our lives. At moments we do not expect, at moments when we feel most abandoned, the entire history of our faith records examples of God's unexpected intervention.
We can never know. We know that God may not intervene when we want but God always intervenes at the perfect moment. The exact moment that is best.
We must therefore remain vigilant, trusting, waiting, exercising the virtue of hope.