OK, OK, I know what's going on. I read some of the possible side effects of Zyban—sleeplessness, jitters, drymouth—Oh! Zyban is speed! I get it now.
That explains a lot. Most specifically it explains why I feel FAN-tastic until about 5 PM (I take the pill in the morning) and as the sun sets, things begin to look menacing. After I delivered an edited chapter last night, I got an email from the project manager at work that read: "Speedy! Thanks!" I read it like 40 times and became convinced that there was a very suspicious subtext indeed. Does she mean that I delivered it too fast and she thinks the quality will be poor? Or that something is not quite right about the speed with which I deliver my chapters? I was completely unsettled.
Of course, it's OK because for the first three days, you take one Zyban in the morning, but after that, you take one in the morning and one in the early evening, so I don't anticipate any more paranoid crashes like that for a while. The downside is that they're not kidding about the sleeplessness part. I've had insomnia for all three nights I've been on it, and that was with only one pill a day. Today I start the two pills a day regimen. I'd be surprised if I sleep at all tonight, but we'll see.
Why am I doing this again? Oh, right, right, I remember: so I won't die.