My father in law, who does my taxes every year, always says that tax day is the adult iteration of opposite day. Whatever was good for you all year suddenly becomes a liability, while your drama and trauma and failure become valuable. At no time in my life has that been more true than during graduate school.
For 364 days each year, I wish that I did not have to think twice about whether or not to buy a $5 sandwich. On April 15, I embrace my low tax bracket and wait for the government to send me a check. From a tax standpoint, graduate school certainly beats working an entry level job!
Conversely, one of the few good things that happens to graduate students--grant funding--is very bad at tax time. A windfall of a few thousand dollars can add several hundred dollars of tax liability, and without careful financial planning you can end up with a very nasty shock in April. It's imperative to save part of your grant checks to cover taxes.
I'm not delusional. I understand that my tax return effectively subsidizes my labor and empowers my employer to continue paying low wages to graduate students. For one day, though, I conveniently forget this fact. Tax day is a good day!