A boundary is not an instruction that forces another person to behave.
'You are not allowed to get angry' is difficult to enforce. 'If the conversation becomes insulting, I will end it and continue later in writing' describes your own action. That difference makes the boundary practical.
Choose boundaries around access, timing, topics, channels and consequences you can realistically follow rather than creating a long list that depends on the other person agreeing.
Start with the places where you repeatedly abandon your own decision.
Maybe you say you will not answer late-night calls and then pick up every time. You agree to practical contact and end up discussing the relationship for hours. You block, unblock and check again. Those repetitions show where the boundary needs support.
Write the trigger, your planned response and the sentence you will use. Reducing the number of decisions you make in the emotional moment makes consistency easier.
Expect guilt and discomfort when the old pattern depended on access to you.
A boundary can feel wrong simply because it is unfamiliar. If previous limits were met with punishment, withdrawal or accusations, your body may interpret consistency as danger even when the boundary itself is reasonable.
A book focused on boundaries can help with the emotional side of saying no and tolerating another person's disappointment. It is a learning tool, not a safety plan.
Use the least complicated contact method that meets the real need.
If you share responsibilities, total no contact may not be possible. Written communication, limited topics, agreed times or third-party arrangements can sometimes reduce emotional ambiguity. The right option depends on your circumstances.
Where abuse, stalking or coercive control is present, get specialist advice before assuming a generic internet boundary is safe.
Do not explain the boundary more times than the boundary requires.
Over-explaining can become another negotiation. You may keep adding reasons because you hope the other person will finally agree that your boundary is fair. Agreement is not always necessary for a boundary to exist.
Use clear language, repeat it if appropriate, then act consistently. If the other person becomes threatening or intimidating, shift from communication advice to safety support.
Rebuild boundaries in new friendships and relationships too.
Recovery is not only about managing one ex. Notice whether you say yes automatically, hide preferences, fear disappointing people or feel responsible for everyone's mood. Practise small limits with safe people where the stakes are lower.
Healthy connection can tolerate preferences, time apart, disagreement and a no. Community gives you more relationships in which to relearn that experience.