NOTE: I realize there's great privilege in even being able to say/feel like one can say no. But, still, many of us need to. And, those of us who are able to must create and protect space for people who can't as readily (due to career stage, identity, socioeconomic and caregiving constraints, etc.). At the same time, those of us who can should also hold accountable the people who have said no for too long and who owe a debt of collective effort and service to our professional and personal spheres.
There's a lot of advice about reclaiming and guarding your time. There are also mountains of seemingly contradictory advice about how to be productive. But, little of that advice deals with the crux of the issue: how you decide how you spend your time.
If you're anything like me and most of the women I work with or mentor, you want to (a) spend your time on work that matters to you and (b) actually make a difference in your field, in your relationships, in the world. For example, nearly everyone I look up to in academia is running one or more programs that actively strive to change the academy for the better, to make it more inclusive, more responsive, more humane.
But, academia is like most of our systems: it was designed for and by a specific subset of humanity, and there's spectacular inertia and a boggling array of distractions built into the ordinary workings of a university.
It can be hard to discern what you should say yes or no to.
Is serving on faculty senate an opportunity to expand your network and weigh in on important policies? Or is it a black hole eating your time and your enthusiasm for the project of higher ed?
Probably, you should sympathize with grad students in other labs who are overworked, underpaid, neglected, held hostage. But, can you (even surreptitiously) actually mentor them out of the hole? Should you (and can you) intervene more overtly?
Maybe you should apply for a president's office fellowship - you'd be on a first-name basis with upper admin and get some (limited) funding for your pet project to improve the university. Or, will you get sucked into endless advisory meetings where no one will listen to your expertise?
Oh! You can apply for/become the next assistant dean of whatnot, so you have a real influence over how things are run, build connections to upper admin, and finally feel like you're making having an impact. But, you might get subsumed by emails, petty office politics, and just grind raw against the admin machinery.
You can just launch something you think is needed, then ask for forgiveness later. You'll probably get to do that important work for years before anyone asks questions. But, how long can you sustain it (and your collaborators' interest in it) without a budget? Without staff? When will you start to resent and avoid it, even though you don't want to shut it down?
Let's put it another way. For most of my career, I said yes to all the things, risks and time sinks be damned. [1] In the process, thanks to the diverse and (very) meandering career I've had, I encountered a lot of workplaces, types of work, and people I needed to or got to work with. As I've surfaced from my always say yes phase, these past experiences led me to something I call my to-don't list. When these types of requests and opportunities arrive in my inbox (or the hallway at work), I have habituated myself to firm "no, no, nopes" for everything on this list.
You'll have to do some serious reflection to build out your own, assuming mine doesn't suit you perfectly. At a minimum, you'll need to remember situations where you experienced:
Obvious exploitation;
That sinking feeling when you realized you should've said no and don't know how to back out;
Work you are good at but intensely dislike doing;
Work that pretty much anyone could do, but they keep coming to you;
and/or intensive time demands that would not likely be expected of someone else.