Practice saying, "I am acting out of my care for whatever," rather than "I need such and such" 

Caring is what makes us human. Actions coming from our caring in key domains of life produce authentic and satisfying behavior. Needs beyond necessities are created from the cultural voice of the market. As the economists tell us–these needs are insatiable and so we will keep acquired things as long as we have the resources to do so. But the world is finite and incompatible with unlimited consumption. Green goods may be better than others, but cannot avoid this reality. More at John Ehrenfeld.