No Eeyores Rule

A rule where startups should avoid hiring people who are pessimistic, gloomy, depressed in order to prevent decreased morale.
A term first proposed by Jason Calacanis in this tweet -> https://twitter.com/Jason/status/627907240037519360

Employee #1: Jack I really don't think you should hire chris because you know no Eeyores rule.
Nontechnical CEO: Cool. Let's look for another engineer unicorn.