I think I'll call these "Barb's Laws of Quilting". They are kind of like Murphy's Law, but specifically for Quilting.
1. The smaller the amount of a particular fabric that you have for a given project, the more likely it is that you will make a cutting mistake. Conversely, if you have lots, you can slap your ruler down anywhere and the cut will come out perfectly.
2. No matter how cold it is, wearing flannel or fleece while you are quilting is a bad idea. Besides the threads that magnetically attach themselves all over you, small pieces that you've cut for your quilt end up sticking to your forearms and/or elbows. Then you can't find them when you're looking for them. This fact is in no way associated with #3, below.
3. If you lose a piece that you've cut, it will not turn up until after you've already cut a replacement. Or changed the whole design because you don't have enough fabric to replace it. (See #1...)