It can be healthy to have high expectations for yourself if you treat it like a goal and it energizes you. But it can be a real problem when you hold others to your high standard.
For example, we were recently on a three-and-a-half hour flight with our 4 year old and our 14 month old. I frankly expected disaster. My experience is that ages 1 to 2 are the most difficult flying time because they don't get what's going on and they can't sit still.
It actually went fine. But I suspect it was more my low expectations than anything else.
The worst thing we can do is to build up experiences we have no control over—large family vacations, plans with others that we make even years in advance. Then when things don't go according to plan, the fallout can feel devestating—wasn't this supposed to be the experience of a lifetime?
I don't know about you, but I'm always much happier when things are more fun, more pleasant, more exciting than I expected. So I'm gonna focus on keeping reasonable expectations where others are involved and save the really great ones for myself.