Why did Jesus want so many of His miracles kept secret?

Have you ever wondered why Jesus on many occasions instructed people not to talk about the miracles that He performed?  Here is an example.  This one actually made me laugh out loud.  Read it and then I'll tell you why.

Mark 5:36-43(NKJV)

As soon as Jesus heard the word that was spoken, He said to the ruler of the synagogue, “Do not be afraid; only believe.” 

And He permitted no one to follow Him except Peter, James, and John the brother of James. 

Then He came to the house of the ruler of the synagogue, and saw a tumult and those who wept and wailed loudly. 

When He came in, He said to them, “Why make this commotion and weep? The child is not dead, but sleeping.”

And they ridiculed Him. But when He had put them all outside, He took the father and the mother of the child, and those who were with Him, and entered where the child was lying. 

Then He took the child by the hand, and said to her, “Talitha, cumi,” which is translated, “Little girl, I say to you, arise.” 

Immediately the girl arose and walked, for she was twelve years of age. And they were overcome with great amazement. 

But He commanded them strictly that no one should know it, and said that something should be given her to eat.

How exactly are they going to keep it secret?  All those people who thought she was dead, they are going to see here up and walking around.  Are they really going to believe that she was just sleeping when they know that Jesus works miracles?  :)