Some of us, like you Physicist, are naturally happy, but it still takes a conscious effort to decide not to let events outside of our control or people who want to hurt have no or little effect on us. I am one of those people everyone would hate in the morning. No matter what time I get up, which is usually very early, I am excited about the day and energetic and happy. That part is natural to me. Learning to stay focused and positive when events or actions beyond my control start to bring me down is harder. Living through eight years of Clinton was extremely hard for me. ;-)
This year I beat cancer, went through chemo and laughed and joked with friends and family that I hoped to have a crew cut by Christmas... which I have! My son is overseas right now, but I know it will be the happiest day of my life when he returns, which I have faith that he will.
Faith, to me, is what allows me to be happy no matter what. I have been blessed with so many good things in my life and all that befalls or befuddles me just makes me think something better is just around the corner. Of course, I still do have to work at it, but that is the joy... knowing it is there if I reach for it. I wish for every one of my FR friends this expectation of good things, and may the New Year bring all of you just that. :-)
I am a natural depressed worrier. I have to work at allowing God to take some of my burdens. It may be several times in an hour where I have to remind myself that I am not carrying THAT particular burden and find something else to occupy myself with.
I have been very, very blessed. I try to focus on that several times per day. Hoping one day it will become "routine" to feel as happy and peaceful as I ought to feel.