The idea that someone took LSD and "was never the same" is a common trope, but I doubt it's based much on fact. I wrote a paper years ago in college about the difference between what "public education" about LSD said and what the medical literature said (I attended a university with a good medical school and a good medical library), and the short version is that federally-funded "public education" about LSD was mostly a lot of scare stories made up to serve someone's social or political agenda. They had little or no basis in fact.
Things like that get repeated, though. People like to repeat scare stories. I wouldn't be surprised if that's where most of the "never the same" stories come from.
I will admit that I took LSD quite a few times at the end of the 1970s, and that at the peak of that period I spent a month or two in a fairly confused and impressionable state. Someone who had known me before and who encountered me during that period might be forgiven for concluding that I would "never be the same". It was temporary, though.
I gave up on psychedelics and other mind-altering substances by the early 1980s. They were no longer showing me anything new. As the fellow said, once you've gotten the message, it's time to hang up the phone.
The literature that I found in the late 70s made LSD look fairly harmless, as long as you were not already psychotic or close to it. That was peer-reviewed research, though, not news stories. It would have been scandalous at that time for anyone in the mainstream press to suggest that LSD was anything less than the scourge of Western Civilization.
Sometime around the late nineties or early 2000s, respectable researchers began to obtain permission to conduct research with psychedelics again, and have gotten some pretty interesting results, especially in areas like treatment of alcoholism, depression, and anxiety. By the way, they don't seem to be finding a lot of civilization-ending dangers in the process. Judging by the medical literature, they just aren't very dangerous.
As far as I know, based both on personal experience and medical literature, the main dangers from psychedelics are that they can be very disorienting and several of them amplify the experience of emotion. Bad trips mostly seem to be a combination of disorientation and fear, with the disorientation becoming frightening, and the fear amplified by the drug so that it becomes terror.
But bad trips end, just like good ones do.
So if you're going to experiment with them, you want to be in a safe place, in a reasonably sane and calm state of mind, and in the company of trustworthy people who have your best interests in mind--preferably mental-health professionals with some experience with psychedelics, if possible.