The idiom "act one's age" means to behave in a manner that is appropriate for someone of your age. It is often used to tell someone to stop behaving in a childish or immature way and start behaving in a more mature and responsible manner.
For example, if a teenager is acting silly and immature, a parent might say, "You need to act your age and start taking responsibility for your actions." Similarly, if an adult is acting recklessly or irresponsibly, someone might say, "You're not a teenager anymore, it's time to act your age."
This idiom is used to encourage people to behave in a way that is appropriate for their age and to take responsibility for their actions. It can be used in many different situations, such as in the workplace, in social situations, or in personal relationships.
• When I saw the way he was acting, I couldn't help but think he needed to act his age and stop being so immature.
• I think it’s important to act one’s age, especially when you are in a professional setting.
• My grandmother told me to act my age and stop playing video games all day.
• Children should act their age, they should not behave like adults.
• The CEO of the company was criticized for not acting his age during a public event.
• Despite being in his sixties, he continued to act like a teenager, which was both amusing and concerning to those around him.