Task: Categorize the tweet's emotional tone as either 'neutral or no emotion' or identify the presence of one or more of the given emotions (anger, anticipation, disgust, fear, joy, love, optimism, pessimism, sadness, surprise, trust).
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