The only thing I would add to all the above advice is that performing when depressed can be unpleasant because you are more likely than average to believe your performance wasn't very good. I find it's often helpful to sing with a group. An open singing seesion or a friendly choir could be nice. When I lived in Sydney, I was very lucky to be introduced to the Solidarity Choir, which has no auditions and is large and very welcoming. There I could sing in a room full of song and it was lovely. Similarly with rousing sessions, you can be immersed, and take part, in live music - the most therapeutic form to take it in, I firmly believe. Go well.