“How do you know if you’re in over your head in a healthy way as
compared to an unhealthy one?  One entrepreneur gave me a good rule of
thumb for this just yesterday.  He suggested that entrepreneurs follow
an 80/20 rule – they should always feel in command of 80% of the
business, but feel way over their head 20% of the time.  It’s that 20%
stretch that makes it fun and challenging. “

–Boston VC Jeff Bussgang, writing at Seeing Both Sides, about the stretch running a company can create–he’s got some good coping suggestions as well.