这句话的直译为 "It is difficult but interesting."，来源是英语中常用的表达方式之一。
举例：
Learning a new language is difficult but interesting.（学习新语言是困难但有趣的。）
This math problem is difficult but interesting.（这道数学题很难但很有意思。）
Cpmbing a mountain is difficult but interesting.（爬山是困难但有趣的。）