First I think it a good idea to study boundaries. Get yourself any books on the topic and study, study, study. Most of the study should be practice.
Sometimes it is easy to determine what part is your and what part is theirs. But deciding “whose is whose” can often lead to discussion.
Here are my principles.
If it is in my body, it is mine. If it is in yours, it is yours. I believe we all have a bit of an aura, an energy field that extends a bit outside our bodies – 6 – 24 inches. What is in our aura belongs to us. Hugging means moving into each other’s aura/body. Be cautious, kind, and do it by invitation only. Use your boundary skills (“soldiers empowered by the emotion of anger”) to let people in or keep them out of your space.
If it is my property, it is mine. If it is your property, it is yours. Humans (animals) are capable of giving objects the attribute of being part of their body. Consider two dogs and a good bone. This can get tricky. With humans, this is a matter for discussion. When you get divorced, to whom does the family picture album belong? Get’s tricky. I find it very useful for a couple to establish clear lines between these things.
If it is my space, it is mine. If it is your space, it is yours. Humans (animals) are capable of giving a bit of territory (a den, a house, a chair, etc.) the attribute of being part of their body. Consider the doorway to your house or to your room. I find it very useful for a couple to establish clear lines between these spaces.
If it is my feeling, it is mine. If it is your feeling, it is yours. If you are upset, that is yours. If I am upset, it is mine. I am not responsible for your feelings. You are not responsible for my feelings. However, based on the idea that we care about, love each other, we do want to help. This is an area of massive mis-training of children. Parents can easily brainwash a kid into thinking they are responsible for their parent’s feelings. The learning phrase is “No on can make anyone feel anything.”
If it is my thinking, it is mine. If it is your thinking, it is yours. I have no right to your thinking, but I will feel safer if you let me in. You have no right to my thinking, but I can help you feel safer if I keep you up-to-date. The learning phrase is “All people make sense all the time.”
If it is my time, I get to spend it as I want. If it is your time, you get to spend it as you want. Here is the ugly issue of Pushing, and Clingers and Avoiders, because we all operate at different speeds.
If it is mine, I do it or take care of it; if it is hers, she does it or takes care of it; if it is not clear “whose is whose,” we take our time (Time Boundary) and dialogue about it; if it is hers and she wants me to do it, we dialogue; if it is mine and I want her to do it, we dialogue.
I am not obliged to do anything for you and you are not obliged to do anything for me. If I do it, it has to be something I want to do, and has to come out of a sense of generosity. See Problem with Expectations.
share our points of view, safely and repeatedly, until we discover or stumble upon a Win-Win (not a compromise). Resistance is a cue for more dialogue. Very little is done until the Win-Win appears.