happy camper
Someone who is happy or content. Often used in the negative to indicate someone who is particularly unhappy, irritable, or displeased. I just got a raise, so I'm a happy camper today. I could tell the crew members were not happy campers after having to work so late. She was not a happy camper when her work permit application was denied.
a happy camper
If you say that someone is a happy camper, you mean that they pleased about something. When Oisin scored that goal I was a happy camper again. Note: You can also say that someone is not a happy camper if they are angry, upset or not satisfied about something. I just wasn't a happy camper. I felt a piece of me was missing and I didn't know what it was.