Why am I happy all the time?

Ok,that wasn't the question I was asked. I was asked "How are you happy all the time?". When did I allow anybody to watch me all the time to come to such conclusions?
Yeah, I was asked that question enough times by now to make me believe that I belong to "ever optimistic appearing" gang. Is it good? Most probably it is, going by the manner in which I was asked that question.
Truth is , I am scared to be worried. I don't like to see sad faces. I don't like to see opaque faces, which compell me to play mind games to find out what's going on in mind of other persons. I like to be happy, relaxed whatever be the situation. And I want others around me too to be in similar state.
Yes, there are situations when I am tense/worried/depressed. But I don't want to transmit all such diseases to others.
Once when I was listing out all my troubles to a friend, my friend replied. "Look at poor , homeless, physically challenged, sick, discriminated...Do you still feel you have problems to cry about?"
That's it. No, that sermon didn't stop me from imagining that I have issues. I just stopped complaining about them :)
Say you are there with your friends in a forest on a dark night. You are afraid of ghosts? Will you start telling others all ghost stories you know?
//y with life, appear positive to add to collective strength.:)
I know, I am not making much sense today. But who said, I will have to make sense all the time.:)