Learn English – The F-word: Is there a polite but equally emphatic and concise alternative to this specific meaning

Is there a polite but equally emphatic and concise alternative to "Fuck 'em" or "Fuck it"?

I am asking if there is an acceptable alternative to the F-word when it is used particularly to dismiss someone or something or to express indifference or nonchalance. I want a word or a short phrase that is somewhat equivalent to

Stop thinking about what others are going to think, and just do your thing …

But I want it to be as powerful as "Fuck 'em" or "Fuck it". Note that this specific use of the F-word does not have any connotation of "anger" or "ill-intentions". Instead, I would say that it shows the speaker "cares" about the person they are talking to.

Polite ways to express the intended meaning includes

1. Don't worry about it (them), it (they) isn't (aren't) important.
2. Listen, just forget about it (them), and focus on …
3. Just don't think about them, who cares about what they want/think! Stay away from the naysayers.

But these don't have the power and the impact that I am looking for. Compare "Fuck 'em! I know what you got, now let's go and get it done!"

Example of the usage in an informal setting:

Coach to student: Hey, you got this beautiful beach near your house, why don't you go for a run and shadowbox there early in the morning?

Student: What?! Shadowbox in public? People are gonna to laugh at me, probably gonna think I am crazy, or that I am showing off.

Coach: Listen, what is wrong with you? How you gonna get naked and fight in the ring in front of thousands of people, with the light shining on you, if you are so bothered with what a few people will think watching you shadowbox in the beach? Listen, fuck what everybody is gonna say or think, just fuck 'em. You go and do your thing, the whole world is your gym.

Now, this use of the F-word is perfectly fine for an informal setting. But I would like to know if there is an alternative for a more professional and formal setting. The alternative does not have to be formal; it can be a mild curse word/phrase too. It just needs to not have the F-word in it and still be effective and powerful.