Debates over egalitarianism for the most part are not concerned with constraints on achieving an egalitarian society, beyond discussions of the deficiencies of egalitarian theory itself. This paper looks beyond objections to egalitarianism as such and investigates the relevant psychological processes motivating people to resist various aspects of egalitarianism. I argue for two theses, one normative and one descriptive. The normative thesis holds that egalitarians must take psychological constraints into account when constructing egalitarian ideals. I draw from non-ideal theories in political philosophy, which aim to construct moral goals with current social and political constraints in mind, to argue that human psychology must be part of a non-ideal theory of egalitarianism. The descriptive thesis holds that the most fundamental psychological challenge to egalitarian ideals comes from what are called Just World Beliefs. A troubling result of Just World Beliefs, one that poses a prima facie obstacle to egalitarianism, is that people tend to dismiss or explain away any threats to their belief that the world is fundamentally just. The pervasiveness and severity of Just World Beliefs predicts that people will be resistant to egalitarian policies. My aim is to show how research on Just World Beliefs can help diagnose common problems for egalitarianism and assist in making realistic recommendations for bringing current societies closer to egalitarian ideals.