I have a partner who is struck by life problems emotionally much more deeper than me. Whenever a setback or tragedy occurs, my partner cries about it and is sad for a long time. Although I have empathy for him and I express it, I cannot make myself terribly sad about it and wallow in self-pity. I accept the cards I have been dealt in life and try to move on.
Because of my mentality, even if I express my sympathy, it is often not enough. My partner often complains: "I wish you also were sad, that would make me feel better. Why aren't you as upset/sad/angry about this as I am?"
Maybe my partner needs me also to be sad to normalize his own sadness. I don't know. I am not sure what to do, because I follow a Stoic philosophy (which also means I do not show extreme jubilation when something good happens, which my partner also finds strange -- but in this case doesn't complain).
So my question is: How do I deal with situations in which my empathy is not enough?