Hey Gastronaut!
I don’t know how much wisdom there is in what I have to say, and I’m not even sure whether I can answer all of your questions…
But I’ve been in and out of depressions all of my life, the last years have been much easier and there are a few things I’ve learned:

1. Passion & emotion are not there all the time, so don’t get afraid when they are missing – they’ll come back! I really get afraid when I recognise that conversations mean nothing to me, that I don’t care about anything in my life and am not motivated to do anything… I am afraid that I will lose what I have worked so hard for. But I have learned to accept it, and I know that I can take my time with myself and that I can go out again when I’m ready – there is no sense in forcing yourself.

2.If you don’t have meaningful relationships yet, fake it til you make it is a very good advise 🙂 Another one is listening. Just listen, don’t judge, don’t think about yourself – just listen. The rest often follows. Look out for people who share the same experiences – it can be hard to connect with people who don’t get your depression at all…

3. Exercise
Maybe I’m lucky in having discipline, but I was not a sporty person at school. I started out of desperation and loneliness… Once your body gets used to it, it is the best you can do to fight downs. Maybe you linger in self-pity for a few days, but a trained body will get you going again and help you out of it. It makes you happy, proud, balanced, and also mentally stronger.

4. Lower your expectations. (Acceptance)
I read a study that depressed people often fail at little things. They get easily frustrated and take things personally… so they give up easily, they blame themselves and the world instead of just dealing with it the way it is.
Things don’t work, things can be difficult, so I think its important to understand that even if something does not work right away its not necessarily a huge problem, and that there is usually some sort of solution for it, it might just take time and a bit more effort. This works for situations and electronical devices 🙂 as well as for relationships. They are never perfect, so don’t expect them to be, don’t expect yourself to be, and you’ll be much happier!

5. Persistance
It takes a long time to rewire your brain. As in 4. – don’t give up, even if there are bumps in the road! They are alla part of lifes rich tapestry 😉

Good luck, I’m looking forward to what others have to write about this… :)))