The idea of someone's 'shoes' representing his life or position dates back to the 1500s. It is usually employed in a negative sense, as in: "I wouldn't like to be in your shoes when he finds out!" It is also used in other situations such as "waiting to fill dead men's shoes", meaning you'll get promotion only when old so-and-so passes on. It simply means that you are imagining yourself in the other person's place.