人生沒有用不到的經歷

過去完成式與過去式同時出現於一個句子，或兩者同時出現於相鄰之句子以表達因果關係時，過去完成式之時間應發生於過去式之前。 以下的例句是寫作時常犯之錯誤：
The liver and paraaortic lymph nodes were involved, so palliative chemotherapy had been done.
應改為 The liver and paraaortic lymph nodes had been involved, so palliative chemotherapy was done. 先有癌症轉移，才會有化療。

The abdominal echography showed that the biliary tree was obstructed by an unknown mass lesion, so PTCD had been done to drain the bile juice.
應改為 The abdominal echography showed that the biliary tree had been obstructed by an unknown mass lesion, so PTCD was done to drain the bile juice. 先有膽道阻塞，才會做PTCD。

過去完成式切忌接某一 "點" 時間，例如
in June this year.

in August 1997.
on June 14 last year.

PTCD had been done to drain the bile juice on June 14. 是錯誤之寫法.
PTCD had been done to drain the bile juice by June 14 when he received left lobectomy of the liver. 過去完成式與過去式搭配：PTCD 在先，lobectomy在後 (June 14之前，PTCD就已完成).

PTCD was done to drain the bile juice on June 14. 過去式才能接某一 "點" 時間.