If only I had gone by taxi.

我要是乘出租车去就好了。

《牛津词典》

If only I knew her name.

我要是知道她的名字就好了。

《牛津词典》

If only I were rich.

但愿我很富有。

《牛津词典》

If only I could find a diamond that weighs one hundred forty carats!"

VOA: special.2009.07.18

If only I had chosen to become a doctor, instead of having chosen to become a lawyer.

要是我选择成为一名医生，而不是选择成为一名律师。

耶鲁公开课 - 死亡课程节选

And there are many people in sort of common sense who might think "Gee, if only I could just use my rationality, think reasonably and rationally and not let my emotions guide my behavior I'd be much better off."

有许多有常识的人,也许会想,要是我能用我的理性，合理思考,不让情感指导行为,我会做得更好“

耶鲁公开课 - 心理学导论课程节选

If only I were a multimillionaire who never had to think about working ever again!

FORBES: Why Shania Twain Can't Sing

If only I could find that woman, I'd hire her one more time just to revive the memory.

CNN: A Latina mom's baby-sitting lament

If only I had learned a trade before coming to the United States, like plumbing, or home renovation, or Qigong.

NEWYORKER: The House Behind a Weeping Cherry