Richard Branson has said on more than one occasion that he wouldn't have been able to build Virgin without a simple notebook, which he takes with him wherever he goes. (inc.com)
For those of you who would probably just lose the planner and get even more stressed out, look into buying a simple notebook. (relevantmagazine.com)
I have lots of to - make lists from a simple notebook to scraps of paper stuffed in my bag to my smartphone. (lastingredient.com)