 Effective choice over time can be extremely difficult given certain challenging choice situations or problematic preference structures, such as the ones described below. As will become apparent, these choice situations or preference structures can prompt a series of decisions that serve one’s large-scale, ongoing concerns very badly. (Note that, as is standard in dynamic choice theory, the discussion in this entry leaves room for non-selfish preferences and concerns; it thus leaves room for the possibility that one can be determined to serve one’s preferences and concerns as well as possible without being an egoist.)