As human beings we are effected by the vibrations of sounds. Our words are based on the combination of sounds that represent a thought. In other words, what you say is a reflection or mirror of your thoughts. You express your thoughts in words.
You have heard the old cliché, "be careful what you wish for, you just may get it." It may seem at times that words almost take on a life of their own. This is because they are in a sense. When you read words you create an internal representation of it. Much in the same way if you chose to say things like “I just look at a piece of cake and gain five pounds”, you are creating an internal response to the words themselves. You chose that statement and soon it becomes ingrained into your unconscious mind. The unconscious mind then begins to respond to it.