You are who your friends are. You are what you eat. If indeed you are a sum of the material world you exist in, then you live in a box with demarcated borders. If you stray beyond these markers, then you no longer are. Or, you're some sort of anomaly.
If you're a beluga, foie gras eating type, then it makes you a person with the means to afford them. If your friends are car-owning, party-everyday type, then it makes you a person with the means to be able to party your brains out each time you would want to do so with these friends.
Your world revolves around the material conditions in which you live. Your points of view are dictated by it. Your beliefs, the things you hold dear, your opinions, your ideas, your wants, your desires, your taste in music, clothing, entertainment. Even the way you choose the people around you, your friends, is dictated by it.
A thought would occur to you because the world in which you exist permits it to be so. Is there nothing more oppressive than this? Is there nothing more delimiting to allow your physical surroundings to dictate your life? But it is a struggle to venture beyond our boxes. No one would want to endure the discomfort of being in a place where one need not be.