Statistical rationalism based on relevant history.

That assumes that the statistics are sufficiently knowable and predictive, and the courses actionable, and that gathering of the information isn't counterproductive, and of course, 'relevant history' is subjective. Pursuing statistically rational behavior might not actually bear out to be a statistically rational approach. :)

Well that's terrifying. To be human is to be utterly incapable of rationality.

And equally as incapable of irrationality as well. :) We can only feign the absence of our own logic.

I haven't met a pessimist that seems to be better off for it. Even so, mitigation requires time and energy as much as anything else, and can take many forms. For example, you could mitigate against loss of a valuable item of jewelry by never wearing it, by earning enough money to replace it, or a number of other ways. To say that you are preparing isn't enough, as there are endless ways in which you can prepare, and those determine how you will be spending your time. Mitigation also requires prioritization of which problems you are going to mitigate for, and those kinds of judgement calls are fraught with subjectivity. You only have so much time, and every thing you do requires that you do not do many others. For these reasons, a pessimist doesn't have much advantage to an optimist when it comes to rationality.

Yes, but adaptation is easier/more effective if the circumstance can be predicted.

To the extent that they can be, and to the extent that the costs of preparation and anticipation don't make life more difficult in other ways.

Again, do things that take your eye off the firing squad. Fill the time until you die of a cause that's socially acceptable, after having paid all your bills of course.

A firing squad? I'm a flash of consciousness on a mote of dust on an island in a sea of time. Social acceptability and bills don't define my situation very well. This all might be lamentable, but water is wet; it could just as well be wondrous.