I see the overall life- health as being a bigger issue than optimist or pessimist.
If people pretty much feel in control of their life and if they are self actualized, I would bet those people come off as optimists. But to me, its a richer and more complex thing.
I do know that Even though I consider myself largely a pessimist, I am also content with my life. I usually laugh once a day (and probably get mad once a day!) The husband here and the dog here generate the laughs. Also, irony in life--always good for a chuckle.