Astronomy? Astrono-you-suck!

Confusion: I know that the Bible says to "rejoice in the Lord always," but is it really possible to rejoice when you've had a truly terrible day?

Situation: Last night, I stayed up late and got up early today to study for my Astronomy midterm. I was feeling great...until I walked into the classroom and all knowledge of astronomy (along with any stamina I had) exited my body. I bombed the test, and while I was walking back from class to a sinkful of dirty dishes and an empty fridge in my apartment, the following thought process ensued:
"I can't believe I bombed it...I actually studied for this one, and that turned out to be my downfall...This sucks...Maybe I should have prayed about it...yeah right, like God would give me the answers, when's it ever easy like that?...God wouldn't have failed it, He made the universe...I'm tired. I'm hungry. I didn't get any mail today. I have to do laundry. My foot hurts....::grumble, grumble, grumble::"

Conclusion: I'm probably going to look back on this in a few days and laugh at the utter absurdity of it all, but for the moment it brings up a good point--do we really have to rejoice through everything? I could have stopped my monologue of self pity today and jumped for joy across campus shouting "I'm so glad the Lord is good!!!!" but I didn't. Should I have? Would other people have? Can you honestly say that when the year isn't what you thought it'd be, you just got dumped, you're falling behind at work, you're recovering from a cold, your foot hurts--whatever ails you--that you honestly feel like rejoicing? Even Jesus wept when he found out Lazarus died....

I'd like to think that God was walking beside me (perhaps limping in sympathy) saying "Boy, that test was a beast!" Maybe I can take my shredded cheese and iced tea in the fridge and perform a miracle like the loaves and fishes. Or maybe I'll just take a nap.