(With apologies to Karl Barth.)
The word "no" is a fact of life for a scientist. The whole point of peer review is to have an anonymous set of scientists read your research and look for any way possible to say "no." They assume what you're telling them is true, but within those bounds they push until they find a reason to say "no."
(This is one of the reasons Richard Dawkins is so strident: he is "peer reviewing" God. Take note that the very phrase is problematic and shows that he's making a category mistake. But it explains his demeanor at least, even if I think he's completely wrong about it.)
That simple fact is one of the hardest but also most valuable things about being a scientist. You're told "no" a lot in one area of life, and you learn not to mind it so much when it happens in other areas. When I'm in a committee or council meeting of some sort of a "no" comes up, it still bothers me, but I push back with my own argument, to see if the "no" can change into a "yes." Because that's the other thing about being a scientist: if you have enough evidence you can force a "no" to become a "yes." Sometimes it's far more evidence than it should take, and it only applies to scientifically reducible categories, but you can theoretically do it. So the "no" is more of an invitation to keep knocking on the judge's door at midnight with more evidence, not to slink away and just accept that the other person won't listen to you.
(Note to self: This applies to professional relationships. A different attitude is usually necessary for personal relationships ... But moving on ...)
I've been thinking about many situations where a well-placed "no" would probably have been a good idea. If you have sextuplets and the TV crews want to film you and give you lots of money and a nice house in exchange for your family's soul, consider saying "no" before the expanse of gifts changes EVERYONE involved. If you're a college fighting for applicants and you're tempted to add all sorts of mid-level staff positions to act as tuition-funded concierges and life coaches for students, it may increase the number of students who sign on in good economic times, but consider saying "no" before the times turn bad and then you have a bloated academic product and you have to lay off staff in order to keep it moving. (This is not necessarily my college, it's colleges across the country according to the Chronicle of Higher Ed.) If you're in any institution with a leader who focuses on "vision," no matter how high or how noble the vision, make sure there's someone there to occasionally say "no" to him or her -- a Roy Disney to their Walt. Etcetra ad infinitum.
(To quote U2's song "So Cruel": "I gave you everything you ever wanted // It wasn't what you wanted")
This is why Simon Cowell and Suze Orman are famous (I don't think it's for their fashion sense). Both have simple shticks.* They can and do say "no" to people, many of whom act as if they've never heard the word before. Good for Simon and Suze, as far as it goes. We need more "no"s so that "yes" retains some value.
* (After watching two or three of her "Can I Afford It" segments, it's pretty easy to come up with a formula that Suzy follows to say "Approved" or "Denied": 8 mo's emergency fund? Retirement OK for age? No outstanding credit card debt? Anyone can guess 9 times out of 10 what she'll say based on those three numbers.)