Interesting discussion.
I consider myself a "selective stocker" in most aspects of my life. I am very much bothered by clutter and like neat cupboards and closets, so as a general habit, before I buy or even accept anything for free, I ask myself where would I put it?
That being said, I love the freedom of spontaniousity, that is thinking up of a quilt pattern on a whim and just go into the closet, find fabrics and start cutting and sewing or in case of the kitchen, open fridge and pantry, collect ingredients and start cooking. I hate to interrupt my creative drive with a drive to the store. So I tend to plan things in my sewing room and kitchen, and buy things I know I will use and organize them neatly that I always know what I have and can easily find it. My sewing room and kitchen are my two favorite rooms in the house!
As far as scraps and leftovers, being an obsessive planner, I plan those too, lol, depending on the dish I plan whether we will have leftovers or not, and with a quilt pattern, I plan how to incorporate scraps in quilts as I go. That being said, if things happen and I end up with leftover, I never throw them away, we eat them, and if I have scraps that I don't have plans form I give them away.