Task: Assess the emotional content of the tweet and classify 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 best represent the tweeter's mental state.
Tweet: Regret for the things we did can be tempered by time; it is regret for the things we did not do that is inconsolable.  Sydney J. Harris
This tweet contains emotions: 
optimism, sadness