Yes, we are all going to die sooner or later, and all civilisations will fail sooner or later (if for no other reason, the cosmos will eventually succumb to entropy). In any case, I'd rather go with later than sooner, and I think worrying about it might help.
I think it's fair to say that some civilisations probably failed due to events that were beyond their ability to predict or prevent, but I think it's also fair to say that other civilisations probably failed due to events that they could have predicted and prevented, if only they'd worried more. Rapanui (Easter Island) and the Roman Empire are a couple of examples of cases that might fall into the latter category.
There are also disasters such as plagues and fires, etc. that have been pretty damaging, but not civilisation ending. In my country, a city was hit by an earthquake a while back, that caused a lot of damage. Building codes are stricter now, because people are more worried about it, and think this might help.
I always wear a seat belt when travelling by car, and in almost every case it's been an unnecessary precaution, and then one day, it wasn't. I've had vaccinations, which were possibly unnecessary, I don't know. My country, like most, has armed forces which spend most of their time /not/ fighting off foreign invaders.
We don't have complete knowledge, so we do risk management. We estimate, or just guess, the probability of an event, it's severity if it did happen, and the costs and benefits of preparations for it, and act accordingly. I think we should, even if the events usually don't happen, because one day, one might.