Drop by a local stationery store and pick up a loose-leaf notebook, and a supply of paper. We've always picked up a supply of index tabs at the same time - either to separate the months or the accountability sections for each item we sell.
The best thing to do for anybody in this catastrophe is to swallow their pride and admit they screwed up. Just face it head on! Admit that you were so proud of your accomplishments that your mind became diluted with "visions of sugar plums and fantasyland."
If your business is a sole proprietorship, you don't have much to worry about really, because as an individual you have three days to think about your purchase, and then to nullify that purchase if you think you don't really need it or can't afford it.