Task: Categorize the tweet's emotional expression, classifying it as either 'neutral or no emotion' or as one or more of the specified emotions (anger, anticipation, disgust, fear, joy, love, optimism, pessimism, sadness, surprise, trust) that reflect the tweeter's state of mind.
Tweet: I feel ghastly and I'm really hoping it's just a post-birthday slump. Back to full research mode tomorrow either way.
This tweet contains emotions: 
anticipation, disgust, fear, optimism, sadness