I was reading The Manager's Path by Camille Fournier and found this gem on page 111:
Saying no to your boss rarely looks like a simple "no" when you're a manager. Instead, it looks like the "yes, and" technique of improvisational comedy. "Yes, we can do that project, and all we will need to do is delay the start of this other project that is currently on the roadmap". Responding with positivity while still articulating the boundaries of reality will get you into the major leagues of senior leadership.
This is a far more elegant way to describe what I was getting at two weeks ago when we talked about capturing ideas from stakeholders. You accept their suggestion ("yes"), and then inject the realities and trade-offs inherent in that suggestion ("and").
Why 'Yes, and' works
This works because it's changing an adversarial relationship ("no you can't have what you want") to a collaborative one ("let's figure out together how to prioritize things").
It also works because it moves a conversation out of evaluating the single item alone and into moving it into context with everything else on the roadmap.
An item that seems easy and valuable in isolation may seem far less valuable when compared to everything else that is being worked on. Or it may still appear valuable and worth doing, but until you look at it in context you'll never know.
Practicing 'yes, and'
So how do you practice?
Well, you could go sign up for improv theater classes (which I actually recommend - it's a ton of fun, and I have met a couple director-level people who recommend it as preparation for management).
Or you could find ways to practice this behavior throughout your work day. Attend brainstorming sessions and practice never rejecting an idea up front, but always trying to build on it.
Or if you have a tendency to say "no" to things, even just starting to say "maybe" and exploring the implications out loud will help build this muscle.
This isn't to say become a yes-man or yes-woman. Boundary setting is still super important - in fact, the further you go in your career the more things you'll have to say "no" to.
But particularly when working with stakeholders and your own managers... practice saying "no" by saying "yes", laying out the implications and consequences of a "yes" and letting them make the decision of whether it's actually worth doing. More times than not the answer will be "no", or at leasts "not now".