"Talk is cheap. Show me the code."
- Linus Torvalds
In reality, this clever quip is just Linus' way of telling people to go away. He certainly talks a lot about code he has no intention of writing. (He does write a lot of code, too.)
It's easy for me to outline how a great piece of software X is supposed to function, but I'm still surprised every time how much more work ends up going into the actual implementation compared to the conceptual simplicity of the design. So, similar to "writing is thinking" I believe that "coding is thinking" as well.