Describe your limit
A workable boundary concerns your participation: when you are available, how you are willing to be spoken to, or what you can commit to. Begin with a specific situation instead of a statement about the other person's character.
Choose an action within your control
'You must stop being angry' asks you to control someone else's feelings. 'I will pause this conversation if the shouting continues' describes an action you can take. Use wording you can realistically follow through on. You don't have to make the boundary more dramatic for it to count.
Keep it proportionate
For a scheduling issue, a practical deadline may be enough: 'I can hold Saturday until Thursday evening. After that I will make another plan.' Leave out punishment, mind-reading, and demands for proof of affection. A clear limit does not need to become a long debate about who cares more.
Put safety first
A writing exercise cannot assess coercion, intimidation, or danger. If stating a boundary could put you at risk, seek appropriate support and consider a safety plan with a qualified service. In an immediate emergency, contact local emergency services. You do not have to manage a dangerous situation through better wording alone.