The survival value of conscious experience:

"The survival value of conscious experience lies in the provision of a mechanism to take a second look (one or two hundreds of milliseconds after on-line behavioural responding becomes possible) at something which, in the immediacy of action, has just gone wrong. The wrongness can take the form of an error in a motor program, or simply a departure from the expected state of the environment: something unexpected happens, or something that should have happened does not. The error signal can be specific (this particular subgoal in a motor program has not been reached, or this particular element in the environment has undergone unexpected change); or it can be highly generalised, as in the case of pain[.] Pain, indeed, may reflect a very early stage in the evolution of the error detection mechanism, providing as it does an undifferentiated and universal signal of important (potentially tissue-damaging) error."

Jeffrey Gray - Consciousness