Regret is defined by dictionary.com as, "to feel sorrow or remorse for (an act, fault, disappointment, etc.); to think of with a sense of loss." Feeling regret is only something one can do when thinking about the past, thus not being in the present moment. The present moment is the only place in time where folks can change things. So, what is the purpose of feeling regret?
Everyone has done or said things in their past that they are not proud of. Perceived failures and mistakes can hang around in the psyche and haunt. Since time cannot be rewound, it is often valuable to shift perception around the event that is causing regret.
The things that have happened in the past are the very cornerstones of who you are now. Sure, there are things you probably wish you hadn't done or said, but if you learned one single thing from your error, then why regret it? Perhaps you learned how to say things a little more strategically. Maybe you learned to think more before you speak. Perhaps you learned something about a person in your life that allowed you to adjust something about your relationship. Maybe you learned how to say, "I'm sorry."
If something from your past is plaguing you today, understand that you can either change your behavior or your perspective in order to remedy it. If it is impossible to make amends or reverse a decision you have made, then look at it from a different angle. Did you learn anything positive from it? Did someone in your life learn anything positive from it? Did it have an eventual outcome that was for the best? If your answer to any of these questions was "yes," then make an effort to drop the regret. Everyone does the best they can with what they have at the time.
Chances are, whatever you regret was done or said without malice. Sometimes, we just don't have all of the information we need at the time to make a good decision. Looking back on something with regret is only getting part of the picture. Look harder and you'll find something good that came of the situation, even if it is that you learned not to do something the next time around.
Regrets can be very heavy to carry around and are often accompanied by guilt. With a thoughtful switch in perspective, you can put down this burden and learn to live more fully. It is impossible to be fulfilled when you're already filled with regret.