Background: The Contrast Avoidance Model (CAM) suggests that worry increases and sustains negative emotion to prevent a negative emotional contrast (sharp upward shift in negative emotion) and to increase the probability of a positive contrast (shift toward positive emotion). Method: In Study 1, we experimentally validated momentary assessment items (N=25). In Study 2, participants with generalized anxiety disorder (GAD) (N=31) and controls (N=37) were prompted once per hour regarding their worry, thought valence, and arousal 10x/day for 8 days. Results: Higher worry duration, negative thought valence, and uncontrollable train of thoughts predicted feeling more keyed up concurrently and sustained anxious activation one hour later. More worry, feeling keyed up, and uncontrollable train of thoughts predicted lower likelihood of a negative emotional contrast in thought valence, and higher likelihood of a positive emotional contrast in thought valence one hour later. Conclusions: Findings support the prospective ecological validity of CAM.