Empathy is the ability to put yourself in another persons position and see that position from their point of view. It's not necessarily agreeing with that point of view, it's more about understanding their reason and rationale for that viewpoint and acknowledging that they have the right to their point of view. It's being able to try to understand how another person may feel. It's about acknowledging that a person has the right to feel the way they do, although we may not fully understand why they have those feelings.
I once had a patient my age who was diagnosed with terminal cancer. At times, he would react with anger towards people, including his father who was at his side constantly despite being a target at times for his son's anger. In fact this father never seemed to take his son's outbursts personally, nor did he react to them. He willingly, lovingly, and tenderly provided care for his son. I overheard staff talking about how this patient treated his father and how they thought it was wrong, disrespectful, how he was jerk, blah, blah, blah. As I was listening to what other staff were saying about this situation, I though about how I would feel if I was in this patient's position and than I responded towards the other staff with these thoughts: I told them that if I was in this persons shoes, I'd probably be angry too. This patient is young (29), has a wife and 2 small children (2-3 yrs approximately), and has just been told he's dying. He's never going to be there for all the "firsts" with his kids (ie: first day of school, first day little league, first bike, first school play, etc) nor will he be there to watch them grow and support them through their childhood into their adulthood. He'll never see them marry or have their own children, he's never going to be a grandfather. He's not going to be there for his wife, the person he chose to share his life with through the good, the bad, grow old with, etc, she will have to face the future alone because he will not be there to support her. At 29, this man is being told he has no future. It makes sense that he's angry, he no doubt feels life has dealt him an unfair hand. If this father could, he would take his son's place in a minute, however it is not something he can do. He takes his son's anger, and takes it willingly because right now it is the only thing HE CAN DO for his son.
Other staff had only been looking at the behavior of this patient instead of considering why he was behaving this way. Can I understand why this patient was angry, yes I can. Does it mean I understand what it is like to be diagnosed with a terminal illness, no it does not. There are things about that situation like that I cannot possibly understand. It's also important to acknowledge when you don't understand what another is going through, it allows them the opportunity to tell you. It's about being willing to understand the other person.
I've had a patient where ambulation was important. I understood why the patient didn't want to move, she was in chronic pain along with post-op pain. Personally I've never experienced both chronic pain and post-op pain. The patient blurted out to me: "YOU don't understand what I'm going through! You don't know how I feel! YOU DON'T CARE!" My response was: "Your right, I don't understand what your going through, I can only imagine what you are going through which is certainly not the same thing as fully understanding what you are going through. I also don't understand how you feel, I'm also not telling you how should feel about this, I can only understand what you tell me. However, you are wrong about me not caring. If I didn't care, I would let you lay in that bed and leave you to your own devices. I do care, which is why I'm pushing you to do what I know needs to be done to facilitate your recovery." This exchange totally changed the nurse-patient relationship towards the better. I had a patient that felt free to express how felt with me and we could now work together to facilitate her recovery.
Sympathy is more about commiseration. It's more about sharing mutual feelings. As another poster stated, it's about feeling sorry for another person. In effect, how does feeling sorry for another benefit them? Sometimes it prevents people from doing what needs to be done because they're more concerned with making the person feel worse. Sometimes sympathy causes others to do things for another that may not be to that person's benefit, which can impede their progression forward from a situation. It may cause one to "pamper" or "cater" to another in an effort to make them feel better which may do more harm than good.
Sympathy is usually not very productive, while being empathetic can be.
Sympathy may cause me not change my patient's wound packing because it's such a painful ordeal for that patient.
Empathy will cause me to offer this patient an analgesic prior to doing that wound drsg.
As a nurse, I guess I view empathy as being able to understand, or at least trying to understand my patient, and still being able to do for them what's in their best interests.