You have many teachers, many lessons, many schools. Are you aware of them all? Do you OVERstand the saying of a wise man, "You learn from the cradle to the grave, even unto China"?
One of the schools in your life is the acknowledgement of cycles. Everything in the universe is subject to cycles. Whether the revolution of one around another or the building and destruction of something or the flowing in and flowing out of something else, we all exist within and around cycles.
In our own lives, we cycle at various times depending on how well we have learned our lessons at certain points. Generally, we cycle at 6 months, 2 years, 4 years, 7 years, 13 years, 16 years, 18 years, 21 years, 25 years, 30 years, 35 years, 40 years, 45 years, 52 years, 60 years and so on and so forth. These ages aren't specific to every Human but they represent stages in your life where you become aware of things that didn't apply to you before.
A child who hasn't cycled past 13 wouldn't understand a conversation held by two 16 year old unless their cycle was rushed but then that would throw off the other cycles in that child's life.
A grown up who has cycled past their 40th birthday may wonder why someone who hasn't cycled past their 25th year can't understand why they feel the way they do. The awareness will come.
Understanding cycles comes with patience and since modern society doesn't teach patience, it is something the Human will have to go off and practice on their own.
Patience is the key to the kosmos - sayeth a great Human