I think the whole thing is a problem. People opining on productivity are creating issues where there are none. And I say this as someone who has tried every productivity strategy under the sun. The only one I have found to work is to just do things until the work day is over. See a task, do a task. Think of something, do something. Get email, reply to email. You can call it inbox zero or eat the frog or Nike Just Do It or whatever other name you want to come up with. But I just do things. Productivity techniques are just structure that get in the way. It can be kind of addictive to design this perfect system for how you are going to organize your work and life - but nothing ever sticks. The only thing that sticks is to just do whatever is in front of you.
