Determine the emotional tone of the following 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". Use the provided emotions: anger, anticipation, disgust, fear, joy, love, optimism, pessimism, sadness, surprise, trust. Respond with the emotions you identify or "neutral or no emotion".
optimism, sadness