2 Yet in all this that the Lord did, He instructs us as to the nature of our life here. In this world there is not a man who is not a stranger; though all do not desire to return to their own country. Now by this very journey we are exposed to waves and tempests; but we must needs be at least in the ship. For if there be perils in the ship, without the ship there is certain destruction. For whatever strength of arm he may have who swims in the open sea, yet in time he is carried away and sunk, mastered by the greatness of its waves. Need then there is that we be in the ship, that is, that we be carried in the wood, that we may be able to cross this sea. Now this Wood in which our weakness is carried is the Cross of the Lord, by which we are signed, and delivered from the dangerous tempests of this world. We are exposed to the violence of the waves; but He who helps us is God.
Source: Sermons on Selected Lessons of the New Testament (New Advent)