Jovial: cheerful in mood or disposition.
I try my best to keep a smile on my face, especially out in public. You never know whether you might be the only friendly face someone sees on any given day. Besides that, even if I'm having a bad day, if I smile long enough, I feel better about things.
When I was going through chemo and radiation, all the medical personnel I dealt with, whether at my appointments or during my many hospital stays, would comment on my constant smile and great attitude. My reaction was that the alternative, which I saw as feeling sorry for myself, wasn't all that attractive to me. I guess I'm too optimistic to go down that road.