He came in for help after his attempts to stop smoking by willpower alone failed.

他仅靠毅力戒烟失败后到这里来求助。

《柯林斯英汉双解大词典》

For then we will realize that our lives are not controlled by the whims of fate, but by ourselves, by our own actions, and by our own willpower.

因为到那时我们就会意识到，我们的生活不是由莫测的命运控制的，而是由我们自己、我们自己的行动和我们自己的意志控制的。

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When we think about being self-disciplined, we have a tendency to assume we need to do it all ourselves, by the sheer force of willpower.

当考虑自我约束这件事时，我们总是倾向于想当然地认为我们需要自己去完成这件事，完全依靠意志力。

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The Dragon Boat Festival is a custom seemingly kept going by willpower, surrounded by the remains of a great tradition of endeavour.

BBC: Here be dragons

While some experts argue that people who are obese should simply eat less and exercise more, many physicians who treat obesity say it is driven by biological changes in the body, not lack of willpower.

WSJ: New Diet Pills Offer Option to Off-Label Obesity Drugs

When your brain detects a discrepancy, it reacts by throwing resources at it: attention, effort, deeper processing of information, and willpower.

FORBES: How to Become A Great Finisher