Everyone knows it. Most people use it to mean: work hard and don't worry about outcomes. That's not wrong exactly, but I think it's missing the actual weight of what Krishna is saying.
The Sanskrit is ma phaleshu kadachana — never let the fruits be your motive. The word is phala, fruit. And this isn't a productivity tip or a stoic reframe on anxiety. Krishna is making a deeper metaphysical claim: the action doesn't ultimately belong to you, because the "you" who would own it is itself a construction.
The detachment he's pointing at isn't emotional distance. It's more radical — it's about dissolving the identity that would be attached in the first place.
Which is why the karma teaching in Chapter 3 can only make sense after the Sankhya teaching in Chapter 2. One without the other sounds like either fatalism or self-help advice.
I tried to work through what karma actually means in the Gita rather than how it gets used in popular spirituality: https://www.wisdomquotes.in/blogs/bhagwat-geeta-chapter-2
What's your reading of it? I'm especially curious whether people find the karma yoga teaching practical or whether it only makes sense as part of the jnana framework.