I know I have talked about learning to say no. I know lots of people I respect on the intertubes have talked about it. For women. For URM. For everyone in a position of little authority. Sometimes we (and I include myself) think it's easy. Just say "no no no" into a mirror every night and you'll be able to do it to the face of the Big Mean BSD leaning on you. What I can say to that, right now is: ha ha ha.
Just like imposter syndrome, there is a vicious little undermining mental loop that says "well, yes, I'll say to the next think I'm asked, but this one is different".
Or in my case: "I'm too old/too senior/too damn good (double hahaha on that one) to say no". Or one of my favorites "this is important to a trainee/former trainee/person I care about, so I won't say no".
And... once again, I find myself finally paying for that hamburger.
I'm writing up a talk, for a professional meeting, on something about which I knew miniscule amounts prior to the talk. Actually I've got two, and I'm only finishing up the first tomorrow (today by the time you are reading this). What an ass I am. You heard it here first.