Elephant Tied With a Small Rope

Once a man was passed from the camp of an elephant. He saw that the elephant is tied with a small weak rope, not with a heavy chain or with a strong rope. He was shocked by seeing this that why the elephant is not tied with a heavy chain or strong rope. He thought that the weaker rope might be broken with a very small effort of the elephant. 
The man became much curious about this. He wanted to know the answer which was rising in the mind of the man. That why the elephant is not trying to break the rope and escape from here. 
The man asked this from the trainer of the elephant standing nearby elephant's camp.
    The trainer replied:
                             "  When this elephant was too small, we tied it with this rope
                                and at that time this rope was enough to hold it . And at
                                   that time, when the elephant tried to break it , it was 
                                   unbreakable for elephant. With the passage of time ,
                                the elephant believed that it is unbreakable for me and 
                                 i can't break it. So, the elephant never tried to break it."
The only reason that the elephant was not trying to break the rope and be free was that he believed that i can't break the rope.

Moral:

 We should continue our struggle by believing it that the thing we are doing is right and it is possible to achieve the goal.If we continue our struggle we will be succeeded one day.