back up the rollercoaster?

Today I was getting thoroughly sick of myself being so whiny and mopy again. I still felt pretty down, but it was a slight improvement. I got to the lab at 10.45! Super early! And I actually managed to talk to my advisor about the tiny bit of work I've done in the past week. The thought of the big batch of stuff he now wants me to do still makes me want to curl up and go to sleep, but I can do the mindless busywork that needs to be done to prepare, at least.
I was going to just go home and hide in my room again tonight, but the tech in my lab who's been applying to grad school kept asking if I was going to the recruiting dinner tonight, so I ended up going along and it was actually fun. I hardly ever see anyone from my program anymore, so it was nice to catch up and the socialising actually made me feel a little better instead of exhausting me, for a change. I didn't even have to hide when I saw someone I kind of know on the bus on the way home, either.
This is another reason I keep thinking I'm making up the depression. I'm back to feeling like I can keep going, without having to hide from my housemates all the time, making my slow, incremental progress and maybe eventually things will get easier. I guess that doesn't sound that happy, but it does feel almost normal.
Now, how long before I end up whining and complaining again? I think the last cycle was a week of feeling okay, two weeks sliding downhill and two weeks being pitiful. I think this okay is still less okay than the last time, though.