You might recall President Bill Clinton's famous quote, "I feel your pain." It suggested that he had empathy and it made him seem more human and in touch with his constituents. Did he really mean it? And, is feeling someone else's pain a good thing, or a bad thing?
Psychologist Mark Davis has suggested that there are 3 important types of empathy. The first is a purely "cognitive" form of empathy that he terms "Perspective-Taking." This is being able to see things from another's point of view. Putting yourself in someone else's shoes. It is important to better understand where someone is coming from, but it's not what we typically think of as empathy.
A second type of empathy, and one that is represented (literally) by Clinton's comment, Davis terms "Personal Distress." Personal distress is literally feeling another's emotions. When you are watching a scary movie, and you start to empathize with the hero and feel afraid, that is personal distress in action. You are actually feeling the other's emotion through a process called "emotional contagion." The actor, or another person, is actually "infecting" you with their emotion. We all experience personal distress, but too much of it may not be a good thing. Some people are so prone to feeling other's emotional states that they are battered about by the feelings and emotions of others (thus the label of "distress").
Bill Clinton didn't really mean that he felt someone's pain (i.e., vicariously felt the other's emotion). What he meant was the third type of empathy: Empathic Concern. This type is what we most often think about when we hear the term "empathy." It is the ability to recognize another's emotional state, feel in tune with that emotional state, and if it is a negative/distressful emotion, feel and show appropriate concern.
These 3 types of empathy represent different aspects of our personalities. A person high in perspective-taking may be good at understanding others' points of view, but may not get very involved in others' emotions. An individual high on personal distress will, as suggested, be prone to experience others' emotional states, which has good and not-so-good aspects.
Years ago we conducted a study with hospice nurses caring for terminally-ill patients. What we found was that possessing empathic concern was positively related to the nurses' performance, but personal distress was negatively related. We surmised that if hospice nurses felt their patients' pain (and family members' distress as well), it made them less able to do their job of providing comfort to the patient and family because they had their own emotions that they had to deal with.
In reality, we all have some level of each of the types of empathy. The key is to understand the ways that we are empathic with others, and to realize the strengths and limitations of each type of empathy.