Everybody sets personal boundaries, mostly without even realising. “I will not go out of the house without makeup on” is a boundary. “I will eat 3 cookies and no more” is a boundary.
I encourage my wonderful clients to set boundaries as one way to take control of their stuff. One such wonderful client had more coffee cups than she could handle. So she set herself a boundary. “I will keep only the cups that fit on this shelf. Any more will have to find a home someplace else. I will keep the cups I love the most, toss any that are chipped or cracked, and donate the rest.” Lots of coffee cups were donated to charity that day, and some were tossed. Now when a new cup arrives, another leaves. The simple act of setting a boundary has helped her keep control in her kitchen.