How do you trap a big monkey in a small cage the size of a banana? Easy! You place a banana inside the cage and leave an opening large enough for the monkey’s hand, but not for the banana.
As soon as the monkey grabs the banana, it is trapped! The monkey can set itself free if it lets go of the banana, but it won’t. By not giving up what it has in its hand, it locks itself just outside the tiny cage.
People are the same – we hold many “bananas” that keep us trapped in little “cages” – because we just won’t let go.