Sympathy: I feel sorry for you
Empathy: I can understand what you must be going through
Respect: I admire the way you are handling this
To sympathise, is to start with the basic. You could even lie through it. And when the hard times are over, you do not need to stay with the emotion.
To empathise, is to go to the next level. You can rarely lie about it. And when hard times are over, you would have struck a chord with the person, because you understood them when very few did.
To respect, is be at the highest level. You can lie all you want, but it instantly shows. And when hard times are over, this grows even further. Because you saw the worst of the person and still stayed.
To respect is to empathise. To empathise is to be capable of sympathy.