So, a couple of years ago (my, how time flies!) I wrote this article, questioning whether some kind of personal damage or substance abuse problem was a prerequisite for good writing. As someone who used to do her best writing buzzed, drunk or miserable, I thought it seemed pretty likely - and research was certainly on my side; so many of the "greats" battled depression and/or drug and alcohol abuse. Of course, when I wrote that article, I wasn't exactly happy. I wasn't unhappy, as such, but, on the surface, my life was missing most of the things that I felt it needed (IE my own place, a decent job, somewhere to write) and one of the things that I knew I wanted (wuv, twoo wuv), so overall, the best I could call myself was discontent. Having been to both ends of the happiness spectrum, I have reached a conclusion:
Writing sad is easier. Writing happy is better.
The quality of one's writing relies on other factors, skill and effort, to be exact. Strong emotions and strong emotional memory are definitely mixed in there, but I think for fiction writers especially, writing should generate emotion, not the other way around.
I write easier when I feel dissatisfied or ill-at-ease. Words just seem to pour out of me then, whereas, when I'm happy and feeling generally content, it's more of a struggle. One of the pluses to being human, though, is that we're never satisfied, not really. The human race never would have progressed if we could be satisfied with just food and shelter. We would still be living in caves. But we're built to want more, no matter what we have (iPhones are a perfect example of this; how can a phone which takes pictures, allows you to edit them, has Internet access, games and lets you watch movies not be good enough? How do they keep marketing new editions of these things?)
So, to clarify, I don't mean that your writing will be better if you're happier, I mean that it's better to write while happy. Because, in the end, your writing will be (or, I should say can and should be) just as good as it would be if you wrote while sad/angry/depressed/drunk, but - and this is the important bit - you'll be happy.