Today is my birthday. Ever since I was young, starting about 5 years old from what I can recall, my internal definition for what "old" was, was 60 years. If they were 50, 40, 30, 18.. they were not “old people."
Today I turned 60 and this is really the first age-based change in perception of myself. I feel like an old person.
(BTW: I also think of myself as more liberal than ever, but self perceptions blind us to our own biases.)