Even well thought out budgets can fall apart. I've done a bit of unplanned spending this month, buying a nightgown and a math book. The nightgown came out of the Amazon gift certificate I got last month, and I might be able to persuade the powers that be that getting better at vector calculus is essential for electromagnetic theory next semester and the book is thus a reimbursable academic expense. It's worth a shot since I've got to go do the paperwork to get paid back for internet access, a modem, and almost $600 worth of lab equipment. I can afford to spend the $11.90 on Div, Grad, Curl and All That if my scholarship won't pay. (Hurrah for used bookstores and ABE Books, even though the internet makes buying books far too convenient and thus tempting).
After reviewing spending patterns from the past two months, I decided to shift some money from my grocery budget into my dining out budget. Now it looks like I'll come in under budget for dining out. I set aside $10 for a geology class Jurassic Park watching party at a pizzeria, but our prof insisted on paying for everyone. The Taco Bell nearest to campus burned down last weekend, dramatically reducing my temptation to buy fast food.