Task: Identify the primary emotion conveyed in the tweet and assign it to either 'neutral or no emotion' or one or more of the provided emotions (anger, anticipation, disgust, fear, joy, love, optimism, pessimism, sadness, surprise, trust) that best capture the tweeter's mental state.
Tweet: Incredibly shocked and disappointed with @united customer service. Really making me rethink flying with them in the future. #unhappy
This tweet contains emotions: 
anger, disgust, pessimism, sadness