I have recently learned that I have synesthesia. It means that my brain automatically connects unrelated senses: it’s like I see the color of a sound, a letter, a day of the week, a year, or some event.
My whole life I thought it was the same for everyone. Apparently, it’s just 4% of the world population that can “hear colors”. My whole life I believed everyone had it the same way - later I learned that only 4% of people have this condition. I was quite impressed.