In today's gospel, Jesus said that "signs will accompany those who believe". We might ask: I have always believed, why haven't I seen any of the "dramatic" signs that Jesus spoke of?
We see that the gospel also says: "They went forth and preached everywhere, while the Lord worked with them and confirmed the word through accompanying signs." (Mark 16:20) God sends signs in order to aid our preaching of the Good News. We must first have enough faith and go out to preach, and at the time He sees fit, He would work with us. This way people will recognize the miracles that we ourselves aren't even conscious of.
Today is the feast of St. Mark, let us "Go into the whole world and proclaim the Gospel to every creature." (Mark 16:15)