Be/act your age
Definition 1 of 1
Pro Tip 1/3Cultural Expectations
Different cultures have varying expectations for how people act at certain ages. 
In some places, it's common to be independent by 18, so act your age and manage your budgets.
Pro Tip 2/3Social Context
Understand the setting, as 'act your age' can mean different behavior in different situations. 
At the formal dinner, when he threw food, his mother whispered sternly, 'Act your age.'
Pro Tip 3/3Emotional Maturity
'Act your age' often implies showing emotional maturity expected from someone your age. 
When he lost the game and sulked, his coach said, 'Come on, act your age.'