一哭二闹三上吊不哭不闹不炫耀
[yī kū èr nào sān shàng diào bù kū bù nào bù xuàn yào]
'Cry, Fuss, Threaten (suicide) if not get what one wants' describes someone being childish. It can also be a complaint that without those exaggerated actions, no attention or good results can be gained, thus no showing off.