Is it more natural to have negative or positive emotions and thoughts?

My meditation this morning was constantly disrupted by little negative, unimportant thoughts. I found it impossible to relax and concentrate and had to give up after only about ten minutes.

My morning walk was then devoted to breathing and concentrating on the beautiful greenery around me, the blue sky dotted with puffy white clouds, and my breath. It cheered me up.

All this made me wonder about our emotions and thoughts and the stream of consciousness we all have. Are we more prone to have negative thoughts? Is it evolutionary? Does the fight or flight syndrome play a part in this?

Or…

Are we more likely to view the world around us and take in the deep positive notions that the universe throws at us constantly? It may be the taste of delicious fruit. It may be a beautiful view or a fragrant flower. There are many things to by positive or even cheerful about.

What do you believe about us as a species? Which is it for you on a personal level? Are we more negative or positive?