Why I can’t develop and design at the same time

I was reading ‘A Whole new Mind’ by Dan Pink today and I found this quote that packaged up nicely my lack of success with developing apps and trying to design them at the same time:

To systematize you need detachment.

In contrast, to design you need to empathize. You can’t envision someone navigating your app and their overall experience while thinking in the sequences and data-driven methods of machines. To immerse yourself with emotional mental tasks and logical mental tasks at the same time is heavy work for both sides of your brain and you often compromise one for the other.