The elephant truly never forgets

The first trick an elephant trainer teaches an elephant is not to escape. When the elephant is still but a baby, the trainer chains the infant's leg to a huge log, so when/if the elephant tries to escape, the log proves stronger and he gives up. Eventually the elephant becomes so used to its captivity, that even when it has grown huge and strong, all the trainer has to do is merely tie the chain around the elephant's leg to anything - even a little tiny twig - and the elephant won't even try to escape.

It has become a prisoner of its past.