Seperation

In this week's reading of Give Praise to God we are told that there does not need to be a dichotomy between driving for dominance and holding onto purity (341). For the most part, I agree, but I wander if there are areas where we need to have absolute, permanent separation. My original feeling is, yes there must be, but what are they? Are there activities that we can never approach? Are there locations that we should never visit?