every decade means a milestone to a person.it depends on one's life experiences.
in china,there is an old saying goes from the Analects.i choose a version of translation to show here.i hope you enjoy it~^o^~
The Master said: “At fifteen, I had my mind bent on learning. At thirty, I stood firm. At forty, I had no doubts. At fifty, I know the decrees of Heaven. At sixty, my ear was an obedient organ for the reception of truth. At seventy, I could follow what my heart desired, without transgressing what was right.”