"Acting Like an Adult" does not necessarily preclude one from behaving like a child, either. Sometimes, an adult must act like a child in order to accomplish what needs to be done.
Older people have every right to be children at heart, enjoying their time on this earth as they please, laughing at silly stories, playing jokes, and looking forward to better days, even if their passing is near.
Not always playing by the rules and taking risks: would that more adults in high places were willing to break past these limits. Much more would be accomplished. Instead or chronic stone-walling, with either side of a conflict merely waiting for the other to fail, both side would offer solutions without vapid reserve.
Acting like an adult sometimes entails acting like a child. Taking direction, admitting that one does not know something. Refusing to cooperate, in some cases, may be perceived as childish, yet in fact demonstrates a determined willingness to be an independent adult,refusing to bow to public pressure or accepted opinion.