To me, it sounds like you're describing a human version of a Golden Retriever. I love Goldens, and people who remind me of them
I mean, intelligence aside, I love people who are happy. I can't stand people who are in a bad mood all the time, who think their lives are total crap and someone is clearly out to get them. That makes me crazy!! I mean, lets take a lesson from our dogs- and just live in the moment. Dogs don't dwell, and although not all dogs are as crazy happy goofy as Goldens (or Pitties are another great example of that personality)- most dogs are pretty happy with what they have.
I am a happy person. I have never been depressed, and its not like nothing bad has ever happened to me. I am just lucky, though- and I know that it isn't controllable for people. I don't expect anyone to be happy when they can't be. However, I find it sick and just plain rude that people would expect ME to tone down my happiness for their sake. Isn't that like, projecting your problems on someone else? I am very bubbly, smiley, and optimistic all the time- and while I do have my moments of being sad, to the outside world I show my happy side even when I'm not happy. Like Jess said- it is how some people cope. I make jokes when something dramatic is happening, and yeah I've been flat out told that I am insensitive- but that is my way of dealing with things. When my grandmother lost her leg to diabetes, we bought her a pirate outfit for halloween. It was hilarious, and she loved it. When my sister went to jail for unpaid parking tickets, we gave her a "get out of jail free" card from monopoly.
Happiness, being bubbly and giddy, doesn't mean someone is unintelligent.