Don't think for others

You don't need to think for another person. Really, you don't. If they behave in a way that is unpleasant for you, you don't need to break your head over why they are doing it (or what you said/did 'wrong'). They considered it possible. And that's it. Want to simplify your life, not waste time? Don't think for others. Think for yourself. What can I do in this situation? (Not what should I do to make them...). You can say that you are uncomfortable. You can ask them not to do it again. You can say what you want and expect. You can suggest something. That's it. This is the boundary. Beyond that, the 'ball' is on the other side. It's the other person's right to decide what to do next - listen to you and meet you halfway or ignore it. Boundaries are where your actual possibilities end, your real 'within my power'. What depends only on me, what can I do? - the first question to ask yourself in any unclear situation.