Goody-goody

You're a goody-goody.

I can't stand those goody-goody types.

Aren't you ashamed of being such a goody-goody, and of studying so hard? You never have a bit of enjoyment.

You know that a marriage isn't always goody-goody, happy.

Tom is such a goody-goody.

I hate being such a goody-goody sometimes.