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: “The #greatest fear #dogs know is the #fear that you will not come back when you go out the #door #without them.”   \n  ―#Stanley #Coren
This tweet contains emotions: 
fear