When I was a little girl my mom would always make our birthday cakes with frosting from scratch. I remember attempting to make frosting one day and asked my mom how much confectioner's sugar and milk to add into the bowl. "As much as you would", she would reply. The problem is, I didn't know how much I would because I'd never done it. I hadn't developed the feel for how much I would, like my mom who had made the frosting at least 100 times - (actually so many more times if you figure nine cakes a year minimum for all of us kids and our dad's birthdays). She just knew. It seemed right. It just felt right.
And that is how I developed my favorite recipes, chocolate chip cookies especially. I just knew how much of each ingredient to add as I played with recipe perfection over the years.
Many times, when we take a risk or leap to attempt something new, it requires a bit of "as much as you would." We don't really know but we tap into our intuition and along with our knowledge and experience are able to figure out the next step forward. It may require tweaking along the way, but with experience we are well on our way to perfection.