“You can always tell them to go to hell tomorrow.” ~ Thomas S. Murphy
If it’s important, it needs to be said. But it might not need to be said right away. You probably have time to craft it properly.
The urgency to speak our minds is often impulsive. Choose the right time and the right way to say it. Just don’t put it off too long if it truly matters.
If it’s a need, frame it as a need—not a demand—and explain your reasons.
If it’s a complaint, aim to get your message across without burning bridges.