Barriers to Compassion 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.
With practice, you can be content by reflecting on the good karma of others rather than joy or happiness. It is very close, if not the same, to praise. For example, if someone you're showing compassion to is now able to feel happy, then you can think "Now this person has the opportunity to practice dhamma since his problems are lesser. This is good". Maybe you can go further and help the person practice dhamma even for a second. This way, you don't cultivate thoughts that nurture attachment, nor do you appreciate any wrong joy or happiness in the other person you helped (such as thanha).