Task: Determine the prevailing emotional tone of the tweet, categorizing it as either 'neutral or no emotion' or as one or more of the given emotions (anger, anticipation, disgust, fear, joy, love, optimism, pessimism, sadness, surprise, trust) that most accurately represent the tweeter's mental state.
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