This document discusses the use of "wish" and "if only" to express regret about present, past, and future situations. It explains that "wish" or "if only" can be used with the past simple tense to express regret about the present, with the past perfect tense to express regret about the past, and with "would" to complain about current or future behaviors. It also notes that "if only" is less common and more emphatic than "wish".