I think modern-day type of sustained, prolonged stress is just not something we've experienced much of prior to x,000 years ago, so there are simply no failure modes evolved yet.
I can't imagine life in the distant past being less stressful.
The modern world has the ability to stress you out over things you can do nothing about (or at least, not very directly and quickly), for long periods of time. Sit down and watch three hours a day for a week of whichever news channel pisses you off the most if you want to see. Some of you reading this already do that, so you may not even notice how pointlessly stressed that makes you because that's how you live. It also has a bunch of other humans who find it advantageous to stress you out that way and bend a lot of time and effort to the task of continually stressing you out, because they prefer that you not be able to carefully think about things but that you react less thoughtfully. You spend more money that way, among other effects.
Past life would spike the stress levels more often, sure, but it generally lacks the low-grade continual stress you can't do anything about. The exceptions that leap to mind (sieges! famine!) would generally be exactly that, exceptions. And in those cases... I'm sure the continual stress of sieges and famines wouldn't be good for them, either!
If your village is raided and you escape harm (quite the assumption), why would you generally return to "baseline"? What if the raiders took all your food and you can't feed your family? What if your family was murdered or raped? What if your village was destroyed and you're now a vagrant?
As I said, when constant persistent stress was occurring, I'm sure it wasn't any better for them than for us. But those were the exceptions. History writes about the famines and the sieges precisely because they're the interesting exceptions. Most people, most of the time, were not in a siege or a famine or under any particular threat from a neighbor.
Today, millions upon millions experience this mid-level persistent stress all the time, for decades. In the 21st century first world, it is the norm, rather than the exception. I don't think that's how it used to be. It especially didn't used to be that way when the danger of famine or siege is as low as it is now, making the stress response even more mal-adaptive.
It was a great summer, can confirm.