mood changers

Some people claim they just wake up angry, before the day has even really started and before they really have anything to be angry about. Some people just wake up happy, glad that it's a new day, or for no reason in particular. But it's the beginning of the day, what is there to be joyful or upset about? I feel I don't have much emotion to express once I wake up, if anything I would just rather go back to bed. However, once I do acknowledge the day and what there is to bring that affects my mood.
Shouldn't that be what it's like for everyone?
If we were to all wear things that indicated our mood and how often it changed I'm sure that thing would be going off the Richter scale in mood swings. I am really interested now as to how much the average person changes their mood, and how many times they go back to the same mood in a day.

Trying to find some information on mood changes, I came across a short quiz. Give it a go, it is kind of interesting. (I'm a tree)
http://www.sam-e.com/learn/quiz?utm_source=google&utm_medium=cpc&utm_term=mood+swings&utm_campaign=Nature+Made+sam-E

Of course our mood is affected by our environment and our diet and sleep patterns, but is there people who are just genetically happier or moodier then others?

"You have about as much choice in some aspects of your personality," Hamer and co-author Peter Copeland write in the introductory chapter, "as you do in the shape of your nose or the size of your feet."

This is regarding personality, but mood is just a step away from personality, isn't it? However, looking further into the article, "specific strips of DNA that appear to influence everything from mood to sexual orientation." is what this Hamer guy was experimenting with. It goes into great depth of this, and other things along the same line.
I found the article at http://www.time.com/time/magazine/article/0,9171,139036,00.html

I also found that there is a relatively popular book on the subject called Mood Genes by Samuel H. Barondes. It seems interesting, and I'm contemplating whether or not I should find it, read it, and then blog about it.

I'll keep you posted.