Take It As It Comes.
I used to freak myself out when I was younger, worrying about handling everything in my disaster scenarios at once, all the ramifications and complications that my fevered mind could imagine. But whenever anything bad actually happened, the reality was always the same: one thing after another that had to get done, one thing after another that I had to accept.
So now when I think, "Oh my God. What if (insert calamity "X" here) happens?, I just answer, "You don't have to figure it out now. There's no way to know how it will unfold. Once it's happening, you will see what needs to be done next and you will do it. And then you will do the next thing and the next thing and the next thing until it is dealt with or you die."
Planning is fine up to a point, it's certainly wise to look ahead and scope out the immediate future a bit, but I find worrying to be mostly a waste of time and energy.
Another thing I've learned is that human beings are incredibly adaptable creatures and that includes me. I have gotten used to all kinds of things that at first were pretty painful and unpleasant. Some of them I even learned to like. I've read accounts of people who endured incredible loss and hardship and still found great joy and meaning in their lives.
Another of the fringe benefits of looking back at past calamities has been the realization that "who I am" is a much more fluid entity than I normally give it credit for being. I tend to think of my preferences and priorities as being more or less hard-wired but disasters have a way of instantly reorganizing them. I've had things that were incredibly important to me become suddenly utterly meaningless and trivial in a split second. Are you going to hold on to that ice cream cone when a car comes screeching around the corner straight at you? I've found it very edifying to learn first hand that some of the things I thought I "needed" were actually luxuries or wants and not needs at all.
So when I imagine some horrible future circumstance, I remind myself that once I'm in that situation, it will not be how I am imagining it now. It will be different. It will be real. There will be one thing after another that needs to get done and I will surrender and adapt in ways that I can't possibly figure out or know about now. I worry a lot less than I used to and I allow myself to enjoy what's happening now a lot more. What comes will come. I will adapt or die trying.