It would be foolish to plan for things that realistically never will happen. For example, as delightful as Douglas Adams’ writing is, one really shouldn’t assume that the Earth could be demolished any time now to make way for a new hyperspace bypass and make plans in case of that eventuality (although it is never entirely a bad idea to have an extra towel or two around).
On the other hand, one would be wise to assume that you will have unexpected expenses that will need to be covered by savings. The roof does wear out, tires and whole cars do need to be replaced, and we all get old.
But one would be wisest to assume that while these expenses may happen, economies are not fail safe, so you should really hedge your bets by stashing your savings in different types of places. So never bet all your pension on the stock of one large company, no matter how solid it seems. Buy bonds to balance out your stock holdings. Have a savings account in addition to your investments, and so on (but really, don’t bury your cash in mason jars in the back yard).
And while you are at it, don’t forget to have a pleasant life. Of course, don’t spend all your money in one place, make sure to save for the rainy day that will come, and make sure your bills are paid, but also make sure you have decent food, nice clothes, a comfortable place to live, all the medicines you are supposed to take, and a bit of fun.