As you eat more hot pepper, you do build a tolerance for it.
Years ago, where I worked, a group of us went to a particular restaurant for lunch several times per week. A guy who worked at a bar across the street from that restaurant came over every day and made a big batch of the best green chili I've ever had. We would always get a cup of green chili to go with every meal we ate there, and that stuff was HOT!
My mouth, innards, and "exit" became used to it, and it didn't bother me in the least. But we took one of the boss men with us one day and encouraged him to try the green chili. He took one bite, and claimed to be in pain the rest of the day and the next morning, as well.
Since I've not been exposed to that stuff, I've lost my tolerance for really hot chilies, and am a "lightweight" again. But I do love the flavors and aromas good chilies can bring to a dish.
I'm pretty sure I would not be able to handle Carolina Reapers!