Negative Thoughts?

It seems to me that humans as a whole are negative creatures. When asking a question it is usually succeeded by a "probably not". In my opinion this can't be good. There are writers out there who are making money teaching people how to be positive. Example: The Secret. But if you have a negative out look on life, can you really be taught to be positive? Aren't human dispositions programmed into our brains from birth? Or is it our environment that supplements our ideas and world views. Well, isn't that the million dollar question. Granted a slew of bad happenings could change the way you view the world. It could implant a me-against-the-world-angsty-teenager view on things. But also it could hinder the way we view positive events in our lives. If we are always expecting the worse then when something good happens there must be a catch. Unfortunately in our society that is how we are taught to live our lives: keep looking over your shoulder because good things just don't happen, you have to work for it. So when someone goes out of their way to be a good Samaritan others get suspicious as to why they are helping. Yet when we feel like people aren't doing enough to help they get ridiculed. It is a nasty cycle that won't stop until it is broken into pieces and not just one person can accomplish such a feat.