I think I'm pretty neutral most of the time, but it doesn't take much to tip my emotions to either extreme anger or extreme happiness...and it's ALL dependant on my mindset.
So, say, while being neutral, I'm browsing facebook and see that some guy wrote something cheeky on the wall of a girl I like, that may mess up my entire week because my mind can't shrug that thought.
Or, maybe if I just happen to get a text message from said girl asking me what i did last weekend, that can make me very happy for the rest of the day.
The things that trigger my 'happy' response aren't really that many (jogging/sports is one BIG one)...so I would say..
I'm neutral 60% of the time, happy 15%, sad 20%, and depressed 5%
Some days/weeks, it's much, much worse