For many people trying to shed a few kilograms, it's hard enough to lose the weight, but many experts say it's even harder to keep the weight off.

VOA: standard.2010.07.30

To use an ancient expression from the 1970's, which only John and I will appreciate, it's really hard to grok what that code is doing, to understand what it's trying to make happen.

我和约翰都会同意，70年代的一句话来概括，那就是很难理解编码的内容，以及它想要完成的工作。

麻省理工公开课 - 计算机科学及编程导论课程节选

With the sports I played, if you're trying too hard in some ways, if you're thinking about it too much, but when you let yourself be in the moment, It's really amazing what happens.

在我参加过的体育项目上，如果某种程度上太过努力，想得太多不可，只有当你在这一刻顺其自然，会发生很奇妙的事情。

普林斯顿公开课 - 人性课程节选

comes from flawed reports of what people eat, because in order to know what people eat you have to ask them, and even if people are really trying hard to be truthful, it's not the easiest thing to do.

这些信息来自于关于人们饮食缺陷的报告,因为你必须询问人们,吃了什么,尽管人们会尽量实事求是,但这很难做到

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选