In my expereince working on core issues is usually painful, at least it has been for me. When in depression I sometimes feel like everything is painful and sturggle to find good things to talk about because when we are depressed it is uaually those painful core issues that cause us the most distress. Sometimes when I go to thereapy every now and then I make it a point to talk about something that I know makes me feel good or it would all be painful. I hope this helps because I struggle with the same thing and know how you might feel.