JADE (Justify, Argue, Defend, Explain)
JADE stands for Justify, Argue, Defend, and Explain, the four things you over-do when you feel you have to earn the right to say no, and the four things a clean boundary does not require.
When saying no feels unsafe, you tend to pile on reasons. You justify the choice, argue your case, defend yourself against an objection that has not even come yet, and explain in more detail than anyone asked for. JADE names that reflex. Each extra word is an attempt to make the other person agree that your no is allowed.
The catch is that explaining hands them the controls. A reason is something to negotiate with. The moment you offer one, the conversation becomes about whether your reason is good enough, and a determined person will argue every point until your no quietly turns into a yes. The more you justify, the more debatable your limit looks.
A clear boundary usually needs less than you think. "I can't make it" is a complete sentence. "That doesn't work for me" does not require a backstory. Dropping JADE can feel rude at first, because over-explaining was how you softened the blow. With practice, the short version starts to feel like respect, for them and for you.