Sashing doesn't just happen when you win a beauty pageant (congrats, btw!). If you love to quilt, you may be doing a lot of sashing, too.
Your quilt looks perfectly fine without a border. But with a border? Masterpiece! That's definitely true when you're using a mitered border — and all you need to know to create this style of fabric frame is how to sew mitered corners.
Truth: If you quilt, you need math. Calculating yardages for borders, backs and bindings is part of the craft, whether you're making the best use of the fabric you have or deciding how much to buy.