This study aims to examine the impact of affective states and affective shifts on ideation and evaluation of creativity. Affects were induced by a two-stage imagination procedure of recalling autobiographical experiences. Three periods of divergent thinking were measured to represent the participants' creative ideation at different times. Creative evaluation was measured by estimating the originality of each response provided by the participants. The results indicate that (a) during the initial period of ideation, groups with positive affect obtain better creative ideation than the groups with neutral or negative affect. (b) The ideation in positive affect groups gradually decreases over time, while the ideation in negative affect groups gradually increases over time. (c) During the evaluation of originality, groups with negative affect have a higher proportion of over-estimates and a lower proportion of under-estimates than groups with positive affect. The viewpoints of cognitive tuning theory, which posit that the affective state influences creativity, are supported.