Decades of research on affective forecasting have shown a persistent intensity bias—a strong tendency by which people overestimate their future hedonic response for positive events and underestimate it for negatives one. While previous research has provided answers on the isolated impact of various individual or contextual factors, this study is original in that it brings them together to determine which ones most influence the inaccuracy of affective forecasting. Participants were asked to predict their emotional satisfaction for a personal life event, the course (positive or negative) and date of which were already known. First, the results support previous research by showing that affective predictions are highly associated with people’s affective experience. Moreover, multiple regression showed that among the individual and contextual factors previously reported to be in relation with affective forecasting inaccuracy, only the valence of the event could explain inaccuracy of forecasting. According to a growing body of literature, these findings point out a tendency to underestimate the intensity of the affect predicted both for negative and positive, with a stronger underestimation for negative events: the negative valence effect.