We've all heard the expression "the customer is always right," but in many workplaces the truth of things is closer to, "the boss is always right." Everyone's salary might ultimately depend on pleasing the customer, but in the tumult of everyday office life, it often feels more urgent to keep the boss happy.

But what if the boss asks you to do something that is in conflict with what's best for the customer? Or what if what your manager wants is stupid, undoable, or simply a massive distraction from what you're actually being paid to accomplish?

You can't simply turn around and tell the person in charge, "No, that's dumb," or, "Get your own coffee, you condescending jerk." But if you comply with the request, you'll be wasting your time, damaging the company, or opening the door to performance-busting resentment.

It's a tricky one, which is probably why someone took to question-and-answer site Quora to ask, "What is the best way to say no to your boss?" Luckily, Madeline Mann, director of people operations at blockchain startup Gem, was on hand to offer advice. In her much upvoted reply, she admits to struggling with saying no before she learned these five battle-tested approaches to set better boundaries with her boss.

1. Use the "Yes, what should I re-prioritize?" method.

If the problem is that your boss is asking you to do more than is humanly possible in a given amount of time, Mann suggests you fight back with this question.

"When someone asks you to do something they often don't realize how busy you are and how not important their ask is compared to everything else you are doing," she explains.This is a polite way to acquaint them with reality. Man offers this quick dialogue from her own experience to illustrate:

Boss:  "Will you make customized agenda and place settings for each person attending the training for tomorrow? That will be such a nice touch."

Man: "Yes, today I am booked up completing info packets, meeting with each vendor to ensure they have everything, and syncing up with each participant - what should I re-prioritize for this?"

Boss: "Oh yes focus on those things, don't worry about the place settings, it's not that important."

That sure beats silently fuming as you burn yourself out working to all hours to do something non-essential, right?

2. Try humor.

When your boss asks you to do something well below your capabilities, or something he could easily do himself, the temptation may to be think, "you're a self-absorbed jerk" while nodding politely and heading off to bring that coffee. Needless to say that's poison for your long-term relationship. But then again, so is bluntly snapping back that you're not a waitress. Rather than getting angry, Mann recommends a gently pointed joke.

For instance, when a colleague asked her to change the temperature on the office thermostat despite the fact he was just as capable of doing it himself, she responded: "Frank, you've got that big genius brain. I have full faith that if you put your mind to it, you can figure out how to change the thermostat. You can DO IT!"

"He chuckled, we had some funny banter back and forth, and then he went over and took care of it himself," she reports.

3. Play teacher

Another approach to time-wasting requests to do tasks your boss could and should do for herself is to re-frame the request for help as a request for information. So if your manager asks you to remind her of the date of that upcoming event, use the request as an occasion to show her where she can find the calendar herself.

"Don't get in the habit of simply telling people what information they ask for, show them how to look it up themselves. I've noticed more often than not that the person I'm teaching truly did not know how to help themselves, and they appreciate me showing them," Mann explains.

4. Pass the baton.

Sometimes the issue isn't that your boss should be handling the ask himself. Instead, it's that he's asking the wrong person. When that happens, just redirect him.

"It's much easier to say 'I can't do it, but X might be interested' than it is to reject a request outright. You are able to come off as being helpful, without having to do the task for yourself," Mann notes.

5. Respond with, "If you can X, then I will Y." 

Finally, if you're handed a massive task that seems well beyond the scope of your role (or the limits of your schedule), Mann suggests whittling it down by handing some of the work back to the asker. Rather than outright reject a task, this phrase allows you to downsize it while still seeming helpful.

"A boss once said to me, 'Madeline you're good at writing, could you write his speech for him?'" she reports. "Instead of taking on such a big task, I modified the ask: 'Totally, how about if he writes the initial draft then I will come in and edit it and punch it up.'"

Running through all these approaches is one fundamental truth: "Just because your boss asks you to do something doesn't mean they require it to happen exactly the way they asked. Protect your time, redefine the ask, and empower yourself to say no'!" Mann urges Quora users.

It's great advice. Unless you are literally an assistant, your job, after all, isn't to make your boss happy. It's to get meaningful work done. Doing more of that sometimes means saying no to your supervisor. If you can't do that when appropriate, you're just not going to be as good at your job as you could be.