I'm British and a journalist, cynicism comes to me a lot more readily than happy happy joy joy thinking. But the kicker for me is that it's quicker to think positively.
You know this already: when things are bad, you spend an awful lot of time brooding. That's too feeble a word: worrying, fretting, chewing, pondering, hating. When things are good, you get on to the next job.
I have also realised that it's true: I shouldn't make decisions and I definitely shouldn't act on them when I'm depressed. I still struggle with the concept of telling myself everything is wonderful all the time but I like the idea of head-down getting-on-with-it-all regardless.
Which is what I take away from this piece on The Simple Dollar about negative thinking:
You have to recognize when you’re telling yourself to make poor choices. For me, the best way to counteract this is to have a checklist of the things you’re working on and review it several times a day.