David, along with his wife Megan, is an excellent runner, and a renowned coach ... and is he also the most positive person in the world? We asked four of his clients what they thought!

"He is very high bandwidth -- making hundreds of runners feel like he's truly their personal coach."

"I'd say he's the most enthusiastically and eternally optimistic person there is when it comes to his athletes."

'He's a low-key savant. And a brilliant environmental lawyer on the side."