Do you ever wonder why miracles don't happen like they did in the days of Jesus? After all, didn't Jesus say that he would be with us until the end of the age? (see Matthew 28:20). And there are other passages that at first glance might lead one to believe that the age of miracles was to extend indefinitely beyond the times of Jesus (e.g. John 14:12). However, note the words of Jesus to his disciples on the eve of his death:
And he said to them, “When I sent you out with no moneybag or knapsack or sandals, did you lack anything?” They said, “Nothing.” He said to them, “But now let the one who has a moneybag take it, and likewise a knapsack. And let the one who has no sword sell his cloak and buy one. For I tell you that this Scripture must be fulfilled in me: ‘And he was numbered with the transgressors.’ For what is written about me has its fulfillment.” And they said, “Look, Lord, here are two swords.” And he said to them, “It is enough.” (Luke 22:35-38, ESV)
These verses seem to be saying that it would be different when Jesus was gone. When he was with them, they didn't have to take a moneybag or knapsack or sandals. They had a special provision during the earthly ministry of Jesus. But after he is gone, they will need these things. They will have to think about provision. Also, during the earthly ministry of Jesus, they had a special protection about them - they didn't need a sword. But this special protection was just that, it was special. It was special to the days of Jesus on the earth. (After all, just a few verses before, Jesus has warned his disciples that some of them would be killed! Luke 21:16-17)
In other words, though we should not sell God short when it comes to working miracles - he has not lessened in power - yet we should not expect the kind of miraculous intervention as we find in the gospels. What God was doing then was authenticating his Son during his earthy ministry through the "works" that he performed (cf. John 5:36). But that day ended 2000 years ago.
This should make us very careful how we read the miracles in the gospels. First, we should not read the miracles in the gospels outside of their historical context. They are not meant to give us hope that every disease in this age will be cured as long as we have enough faith or pray hard enough. We should read the miracles for the purpose for which they were intended: to authenticate the identity of Jesus as the Son of God and Savior of the world. Thus, we should read them as a call to faith in and submission to Jesus Christ. If you say you believe in the miracles of Jesus and yet are not submitting your life to him, then you have missed the point.
Second, we should not read the miracles of Jesus outside of their theological context. The Bible as a whole, including the gospel accounts of the miracles, gladly affirms the sovereignty and power of God over all things. God can take viruses and destroy them. He can take leprosy and speak it out of existence. He can make the blind see and the lame walk. But it also affirms that God owes no man anything. Even Jesus taught that when Israel was full of lepers, only a foreigner - Naaman - was healed (Luke 4:27). God can chose to heal and he can chose not to and be just in both instances.