Are you saying you don't learn anything from thinking through how to write a big piece of code before you write it?
The vast majority of bugs I find after writing the code are trivial. Certainly, I learn something from writing it, but I find that if I just start writing without thinking about it first, especially for larger projects, I don't end up where I want to and have to scrap large pieces of it.
Writing helps you get the details straight, but thinking is essential for designing the big picture.