I think most would say that anger and prejudice are the main obstacles to compassion, but I'm wondering on the topic of sympathetic joy. If everything is empty, and suffering, and impermanent, how can we be happy for the joys of others which are empty, and ultimately suffering? I feel like being happy for a joy which is in fact suffering is like being glad someone took poison. I would like to develop compassion for other's joys--the real joys that will further their lives--but I find most of the things people are satisfied by detrimental things. Any thoughts?
EDIT: Also, I wonder how, since everything is intrinsically empty, one can truly be happy for events occurring to someone else since they have no absolute effects. This would imply one would have to be happy for the happy emotions others have in themselves rather than what occurs, but once again, but Buddha explained these as suffering, even the most blissful states.