Tax season usually brings one of two emotions: the dread of owing or the thrill of the "windfall." If you’re among the millions of Americans expecting a refund this year, your brain is likely already cataloging the possibilities. A tropical getaway? Finally upgrading the living room furniture? That gadget you’ve had in your cart for months? It’s tempting to treat a tax refund like "play money." But before you book those flights or click "buy now," there is one critical projec