Task: Categorize the tweet based on the intensity of the specified emotion E, capturing the tweeter's mental state. 0: no E can be inferred. 1: low amount of E can be inferred. 2: moderate amount of E can be inferred. 3: high amount of E can be inferred.
Tweet: No pessimist ever discovered the secret of the stars,or sailed to an uncharted land,or opened a new doorway for the human spirit.-H.Keller
Emotion: sadness
Intensity class: 