This morning I found a short article that addresses this and also offers some remedies.
Here's one very sensible excerpt:
When you are down and feel low have you noticed how much time you spend revisiting the past, replaying the story of what happened and saying to yourself "if only I had"...or thinking "what if...."? Your emotions are powerful and the way you think, what you think and how you think can enhance or destroy your sense of inner peace and calm.And here is one of the suggested exercises:
Learning to release attachment from your story, your pain or sadness takes practice, courage, confidence and skill. As a human, you are programmed to care and worry, so naturally, if a friend is upset, or your partner falls ill, your natural tendency is to empathise with their pain and to feel sad for them. The trick, or test, is to be able to empathise with someone else's sorrow and pain yet, somehow not to get stressed out and totally worried; otherwise it becomes harder for you to offer support, encouragement and compassionate advice.
Sit on the floor or on a chair with a lighted candle in front of you. Gaze at the flame through half-closed eyes, then close your eyes and visualise the warm glow from the candle behind your eyelids. Stay focused on this image. If you lose the image, gently open your eyes and gaze at the flame, then close your eyes and repeat. Continue with this practice for 5 - 10 minutes.When I was studying at the Tibetan Center in Cape Town we did candle meditation in one of the classes. Each person (and it was a large class!) had his or her own personal candle. Needless to say, this was very powerful done in a large group like that. But it's also truly effective when done all on one's own.
Here's the link for the article: "Three Types of Meditation For Instant Stress Relief From Emotional Pain ". The author is Ntathu Allen. You might like to click through on her name and see all the other articles she's written. Looks like there's a wealth there!