EDIT: Oh stupid... Nevermind. I know what this is. I was late filling a prescription and had to skip a dose of one pill Saturday morning. I was fine yesterday, so I'd forgotten. Agh. Stupid SSRI's and their long time-constants. Oh well, at least I know why, now.
It sounds like what you're on has a shorter half-life than mine, or else it differs by individual metabolisms. I'm always randomly forgetting to take my daily dose, but I've never really noticed any appreciable effects. Glad to hear you figured it out though. 
Thanks. I'm glad too. Knowing that, oh, I'm just off my meds a little, somehow made the fact that I was irrationally despondent a lot easier to bear. Day after I was just fine, too. And yeah, it varies a HUGE amount based on individual metabolic and neurochemical differences. I'm on about the lowest dosages that are available without custom compounding. Everyone's different.
Back on a (relatively) even keel just the same. Home with the kids today because Unit #2 has a cold and we don't want to infect his friends at daycare. Sort of working from home, sort of taking the day off. Partially frustrated at the inability to do most of what I need to do. Partially relieved for the break. Very grateful that I have the luxury of taking time off for the kids if they need me.
You know, I had severe reservations about inflicting my head-case genes onto another generation, but they are really good kids. I still fear this world will eat them alive, but they have a tough and stubborn core underneath that sweet (if mischievous) exterior. I think there is a good chance they'll be on meds before they are old enough to leave home, but I guess I turned out ok for all that.
I guess I'm just taking a moment to consider my lot in life, and really, I have a lot to be thankful for.