What is one ugly truth you learned as you got older?

Most people do not get smarter or wiser as they age — they just get older. I sort of realized that as a kid, but it really hit home as an adult when I mainly had to deal with other adults. Age does not in fact produce wisdom. Often, quite the opposite as people lose their innate curiosity and drive to improve themselves that they possessed when younger. This causes de facto decline.

To put it more crudely, and contrary to popular belief, dumbasses generally stay dumbasses and many get worse as they age, not better.