鸡蛋碰石头 [- - pènɡ shí tou]throw an egg at a rock; an egg itself against a rock; attack sb. far stronger than oneself; like an egg striking a rock — only to cause its own destruction:
•¶ 鸡蛋怎能碰得过石头, 还不是自寻死路。 They're just like eggs hurled against stone; they're heading for their doom.