Act your age? I don’t understand how to do that. There is no handbook that says, “When you are 34, you must cease to be whimsical and quirky. You’ve reached adulthood, responsibility should be your only focus and you should be tame and staunch and stay home every night.”
Instead of saying “act your age,” say “be the best version of yourself,” and then end the discussion right there because no one can really tell another exactly how to do either one of those things anyway.