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: 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