Answer first: say your action, not their rule
"You can't call me after ten" is a demand. "After ten, I'm going to let calls go to voicemail and ring you back in the morning" is a boundary. The second version works even if the other person does not like it, because it only depends on you.
When a boundary is written as a rule for someone else, it turns into a contest: they push, you argue, and the limit becomes a debate about whether your rule is fair. When it is written as your own next step, there is nothing to win. You simply do what you said.
Why the framing matters
Assertiveness, as psychologists describe it, means stating your needs clearly and respectfully without trying to control or punish the other person. A "you must" sentence slides toward control. An "I will" sentence keeps the focus on your own choices, which is the part you can actually keep.
It also lowers the temperature. People tend to hear "you can't" as criticism. "Here's what I'll do" gives them information instead of a verdict, so they have less to defend.
Turn three common demands into actions
- Demand: "Stop showing up without warning." Action: "If you drop by without texting, I'll say hi at the door and we can plan a proper visit."
- Demand: "Don't yell at me." Action: "If the conversation gets loud, I'm going to step out and come back in twenty minutes."
- Demand: "You have to stop borrowing money." Action: "I'm not lending money anymore. I'm happy to help you look at other options."
Each version names a situation, then the one thing you will do. No lecture, no history, no prediction about their character.
Pick an action you will really take
A boundary is only as strong as your follow-through. Before you say it, ask: will I actually do this the first time it is tested? If the honest answer is no, choose a smaller step you can keep. Letting one call go to voicemail is better than threatening to block a number you will never block.
Keep the action proportionate. Stepping out of a heated room is reasonable. Ending a friendship over a missed text is not a boundary; it is an escalation.
Say it once, calmly
Pick a neutral moment, not the middle of the problem. Say the situation and your action in one or two sentences. If they ask why, you can give a short reason ("I sleep badly after late calls"), but you do not need to win agreement. A boundary is information about you, not a proposal that needs a vote.
Then do it without commentary
The first time the situation happens, take the action you named and skip the speech. Let the call go to voicemail. Step out of the loud room. The calm repetition teaches more than a second explanation would.
When the boundary is about safety
If you feel afraid of someone's reaction, or a limit keeps getting crossed in ways that frighten you, an "I will" sentence is not enough on its own. Reach out to someone you trust or a local support service before you set it, and put your safety ahead of the conversation.
Practice for this week
Write down one "you must stop" sentence you have been holding. Rewrite it as "When X happens, I will Y." Read it back and check that Y is something you control and will actually do. That is your boundary.
Questions
Isn't telling someone what I'll do just a threat?
Not when it is calm, proportionate, and something you will really do. A threat is meant to punish; a boundary simply tells the other person how you will look after yourself.
What if they get upset when I say it?
They are allowed to dislike it. You can acknowledge the feeling ("I hear that this is annoying") and still keep your action. You do not need their agreement for the boundary to stand.
Do I have to explain my reasons?
A short reason can help, but a long justification invites debate. One sentence is enough, and "this is what works for me" is a complete reason.
Related guides
Find your own words.
Use Conversation Prep to separate what happened, what matters, and what you want to ask.
Open the worksheetSources & context
- How to Be More Assertive at Work (American Psychological Association) — Assertiveness means expressing needs and limits clearly and respectfully rather than passively or aggressively.
- How to Set Boundaries (Psychology Today) — Boundaries describe what a person will and will not accept and are maintained through their own consistent actions.