Youngling, compared with some of the teens the internet lets one meet in fandom, you're positively old, and I'm ancient. Also, the stress is because of the organisation of the birthdays. I didn't do anything for my 30th and left the country, so this year, I'm due, and there will be a major party on Saturday night. (The birthday is on Sunday.) And a tour through my hometown on the afternoon before that, because it's pretty and a millennium old, and a lot of my friends don't know it. But even someone else's normal birthday isn't, no pun intended, a piece of cake; yesterday I was on my feet all the time organizing food and washing dishes while friends kept dropping in to congratulate my mother. In conclusion: stress.