Why is NBC News soooooo negative and depressing?

I'm normally very optimistic and positive but watching the Nightly News with Brian Williams would depress Norman Vincent Peale. Everything and I mean everything has a negative ring to it. I feel the economy is suffering but why worsen it by reporting only the negative. I listen, waiting for the sky to collapse and fall. Iraq is all but lost, eventhough the troops overwhelming believe their mission is almost completed. When the stockmarket blows past 400+, there is always a but........but the average senior is suffering. Seniors shouldn't be playing the damn market, in my opinion. I know, I should switch channels but it's intriguing to hear his disdain for America and his biased hyperbole.