It's likely the unpredictable uncontrollable and ongoing nature of day-to-day email, in terms of volume, importance, and urgency contributes to their levels of anxiety and to diminished leadership skills.
I'm keenly aware that however much I have accomplished and however hard I work, I could be laid low by a tiny lesion that I can neither see nor control.
And this is where the first habit comes back, stop focusing on what you can't control, and you'll be able to create more, you'll be able to add more value to the world.