I find this a bad advice due to many different reasons. First and foremost, startups must have high expectations in order to, well, start up. People would never, ever create a company assuming it would go straight to hell after six months.
What also bothers me with this statement is that, by keeping expectations low, you would probably not work as much as you would if you had higher expectations.
As a final note, I have always kept my expectations very, very high. I always aim for A's at university. Yet, I do not feel less happy than the average Joe, even though I sometimes get a B or a C.