Notice: Rant warning!
Frankly, this is one of the more irritating takes on poly that I run across! Based on the idea of autonomous hedonistic abandon: There is no one of importance in decision making, outside of yourself, even in situations where multiple partners are impacted by those decisions. The feelings and needs of others are only considered if it's convenient, and fits with what someone naturally, organically, wants to do themselves.
When someone uses the fact that they are poly to justify impolite, inconsiderate, irresponsible, unkind-to-others behavior, it really grates on me. "Well, I wanted to do X, so even though our agreement was that X was off the table, I did it anyways. Stop trying to control me! That's not poly! So there!"
Show a bit of SELF control! Being in relationships involves, well, relating to others. It's not a solo practice. If the objective is complete autonomy, get out of the relationship business. Keep things strictly transactional, so that no one is surprised when you fly off to Hedonism III, instead of showing up for the family vacation.
There are going to be times where saying "no" to yourself involves saying "no" to someone else as well. That sucks. I get it. It'd be nifty keen if we were all independently wealthy, had unlimited time, and there were no conflicts between your partner's schedules and needs. It'd be groovy if all the practicalities of life spontaneously took care of themselves, and no one had to do laundry instead of taking a free class on sensual massage with the Swedish Bikini Team, where they were the demo model.
Life ain't like that! Deal with reality here: Sometimes, saying "no" to yourself in the moment is the best thing you can do to create the opportunity to say "yes" in the future. Sometimes, you just do without, but in the end, if you are surrounded by those you love, and you respect how you've gotten there, isn't that worth telling yourself no?