Task: Evaluate the tweet for emotional cues and classify 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 indicate the tweeter's state of mind.
Tweet: When you burst out crying alone and u realize that no one truly knows how unhappy you really are because you don't want anyone to know
This tweet contains emotions: 
sadness