I interpret this in the sense that your environment is a key driver of your actions.

For me this is most evident when observing where I (/ my friends) live. If you live with people who drink four nights a week, guess what...you probably will too. If you live with people who cook healthy food and go running three times a week there is a much greater chance you will too.

Obviously you can rise above your surroundings but if you have a goal then you should put yourself in an environment conducive to getting there.