I completely understand what you say here about being followed by the Sa cloud and having trouble with seeing others happy. for me personally, things have gone in cycles, and a combination of antidepressants and counceling have insured that my down swings are not as long as they were, and that there are points I can concentrate on other things and even have fun, whether on my own or with others. In a good state, I can be happy that someone else is happy, while in a bad one, it hurts incredibly, ---- especially seeing a close, committed relationship betwene others.
what has helped me is professional counceling, being proscribed citalopram and (occasionally), advice from a couple of very close friends.
of course I'm not you, and my experiences and their effects will be different, but certainly I think there's reason to hope that the Sa cloud won't be consuming your life entirely over a long period.