This is something I noticed while cooking today—and while shopping for groceries and traveling. (Remember traveling?)
If I don't prepare well enough, I end up with more of whatever it is I'm doing. Intuitively, I would have guessed less—not enough time to plan: not enough time to get things: not enough things.
What really happens is that I end up compensating for various possible scenarios, many of which are irrelevant, most of which are unnecessary. In cooking—today, 宫保鸡丁—it manifested itself as cutting more things than I needed, and cooking things longer than necessary. Not sure how much onion you need? Cut a whole onion. Not sure if the chicken is fully cooked? Cook it some more. You won't be wrong—no death by food poisoning, for example—but you won't be right. It's a hedge against catastrophe rather than a drive for victory. The extra onions go in the compost; the extra time on the chicken ruins the texture.
When traveling, not preparing well enough means packing more than is needed. Not prepared to do laundry on a trip? Pack twice as many clothes. Don't know how to use the pharmacy or grocery or whatever where you're going? Pack extra snacks or medicine. Think you're going to exercise every day, pack extra clothes. And so on. I have yet to go on a trip where having more is better. Less isn't more, but less can be better. The extra preparation means you can think more clearly about the edge cases and treat them like edge cases—things that aren't likely to happen. You can still include your hedge for some of them (rain, for example), but a few extra minutes or hours of prep saves a lot of trouble.
A more extreme form of the benefits of preparing comes while backpacking—in the woods or in civilization. When I last went to India ten years ago, I was able to go for more than two months just with carry-on (one small backpack, one camera bag) because I thought about what to take (detergent powder and fewer shirts) and what not to take (no shorts, one pair of shoes). In the woods, it's even easier. If your body odor falls in the forest, and no one is there to smell it, do you stink? It doesn't matter. Two shirts is enough—one to wear, and one to hold pot handles. If you don't prepare enough, you'll end up taking three more shirts which, when rolled up, are the size of three beers, and you need to ask yourself if that's really a trade worth making.
Good preparation is minimization, not maximization.