Yeah, I think GP is right and this all feels like word play to me.
Let's say you're making your ideal wood chair for your living room. You're "fretting" over getting the arms, legs perfectly aligned, surfaces smooth, identical chamfers, etc. But fretting is bad and makes it hard to get anything done so you stop. Then you end up with a roughshod chair.
You shouldn't "fret" too much, but you also shouldn't "fret" too little. You should "fret" exactly the right amount which is... tautologically true, and not particularly insightful. Giving your best is committing yourself to fretting.
(I'm not sure if you understood the Gita reference, if you did you can ignore my comment.)
A better analogy isn't so much a chair made by yourself, but say you're making a chair for a competition. The only thing you can control is your actions. What's out of your control is whether or not some other guy who's an absolute veteran is also planning to compete (making you likely to lose), or if almost no one else joined the contest (much higher chance of winning.)
Another example is in the workplace.
You control what efforts you put in.
But your promotion (or even firing!) depends on a ton of other things. If the company's doing poorly, they may not promote you even if you did a great job. Conversely, if the company desperately needs a new senior person and you're the closest fit, even if you just did a mediocre job, you may get selected.
What's common in both cases is - doing a better job is more likely to be better for you. But there are no guarantees you'll win/get promoted, so don't be attached to that outcome, but only your efforts/labour.
Let's say you're making your ideal wood chair for your living room. You're "fretting" over getting the arms, legs perfectly aligned, surfaces smooth, identical chamfers, etc. But fretting is bad and makes it hard to get anything done so you stop. Then you end up with a roughshod chair.
You shouldn't "fret" too much, but you also shouldn't "fret" too little. You should "fret" exactly the right amount which is... tautologically true, and not particularly insightful. Giving your best is committing yourself to fretting.