It is essential to understand the difference between empathy and sympathy. People often think they are being empathetic when in fact, they aren't.
Why is it important? Because empathy is productive and sympathy is, at best, neutral, at worst, hindering.
Empathy
To feel with someone. If you can achieve empathy, you are able to fully encompass what the other person is feeling and put yourself in their place. It enhances both your understanding of the situation and the person and enables you to discuss things in a useful and productive way. Someone who is being empathetic will tend to ask questions rather than offering solutions, helping the other person reach their own answers. Empathy is about what the other person feels.
Empathy doesn't only address negative feelings, but also positive ones.
Sympathy
To feel for someone. People who are sympathetic tend to consider how they would feel if the same events happened to them, without taking into consideration what makes the other person different from them. They may express pity which is both patronising and may encourage the other person to wallow in their misfortune; or offer advice, but the solutions they give come from their own perspective . Sympathy is about what you feel.
A sympathetic person is often less interested when the news you have for them is good.
The two words should not be used synonymously.