Maybe it's a self-preservation-thing-turned-habit: expect the worst and either be prepared or pleasantly surprised.
But that's the thing: we never seem to be prepared (because that small, still part of us refuses to expect the worst?) and, really, pleasant surprise only lasts as long as we can keep our minds at bay.
So here's the question: when did we become such slaves to the voices in our heads? And tell me this: how often is that voice wrong? How rarely does true disaster strike, despite on-the-hour (or minute) warnings otherwise?
Well. Here's a thought: next time it pipes up, I'll kindly ask it to hold its tongue. If I must, I'll pull out the reams of evidence discounting prior predictions, but a good "shut up" here and there might just do the trick.
It's a learning curve, petals, but we'll get there.