h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

That's pretty much what I've been told, in different phrasing and subtlety, ever since I started accepting that I have depression. I have had it for almost as long as I can remember - I can't really remember a time before I was constantly sad. I had a rough childhood, and that was part of it, but I also have a family history of it.

I've gotten a lot better over the last 9 months or so, with medication and a huge change in lifestyle, but I'm still having trouble with alcohol, my weight, and work. My work is *very* stressful, infinitely more so because of this stupid economic recession. I'm having a lot of trouble continuing to keep up my work, seeing as there's a lot less actual work out there. I've tried explaining how hard it is to make myself stay motivated, but neither my bosses or my coworkers really understand. I've been accused of bringing down the entire office with my sad moods, and told, basically, to smile more.

I know the logical option is to quit, find something less stressful to do, but I'm just out of university, and this job is a great opportunity, with huge rewards (ie, 6 figure salary) when (if) things pick up. Plus, my workmates are the only people I know, besides my (toxic) family and my flatmate, and I don't want to lose them as friends.

So, how can I either get my workmates and bosses to understand that I'm not deliberately being sad? Or should I just put on a brave face and stop talking to anyone about my depression?