Whether it's luck or not, a video showing a scene in Itaewon Class popped up on my Facebook feed. Roughly speaking, the line in the scene is about the importance of using one's time wisely, which I copy-pasted below. (Although, considering each character's situation, you could argue that it's fundamentally about the necessity of believing in yourself -- in order to make time your friend.) I really like how the screenwriter used the words "시간" and "농도" together (see the last line). "시간" is very straightforward -- it means "time." I think the most accurate translation of "농도" for this context would be "density." "하지만 그와 나의 시간은... 그 농도가 너무나도 달랐다" translates to "But his and my time... the density was strikingly different."

"시간이 흐른다.
반복적인 하루. 지겨운 나날.
그렇게 7년이 지났다.
분명 시간은 누구에게나 공평하게 흐른다.
하지만 그와 나의 시간은... 그 농도가 너무나도 달랐다."

-이태원 클라쓰의 명대사 중 하나-