Diamond cut diamond

Diamond cut diamond.
硬碰硬；势均力敌；龙争虎斗。

Cut your coat according to your cloth

Cut your coat according to your cloth.
量布裁衣；量入为出。

Cut not the bough that thou standest upon

Cut not the bough that thou standest(stand?) upon.
不要砍掉你立足的树枝；不可忘恩负义。