Morning
Say the boundary sentence out loud, alone, first
Practice the exact sentence you need to say to someone, alone, before you say it to them
5 min
How to do it
Pick the boundary you've been avoiding stating. Write the sentence in plain words, then say it out loud to an empty room a few times until it sounds normal, not rehearsed. Then say it to the person.
What the evidence says
Rehearsing a difficult statement out loud before saying it for real is a technique drawn from training in speaking up for yourself, with general evidence that practice lowers the nerves of the real conversation and helps you say it more clearly. It doesn't guarantee the other person's response, only how steady you are saying it.