You are so, so thrilled to finally be done with your latest project regarding sales projections for wooden toilet seats in China. So overjoyed, in fact, that a split-second after you save your work, you hit "Print" and stand up and do a little happy dance. A few minutes later you see that you misplaced exactly 60 apostrophes, one on each page you printed.
Now you have to correct and reprint every page. Not only did you waste your presentation-quality paper, but you threw away ink, too. You could have saved on both if you'd just double-checked your document. Just to be safe, maybe even triple-check it.
The same goes for photo printing. Before you commit your pictures to paper, perform at least the most fundamental fixes such as cropping and red-eye removal, to make sure you won't want to immediately discard the results. And use the right paper. Printing a detailed photo out on paper that's not designed for photos may get you nothing more than an inky mess and disappointment.