Personal boundaries or the act of setting boundaries is a life skill that has been popularized by self help authors and support groups since the mid-1980s. Personal boundaries are established by changing one's own response to interpersonal situations, rather than expecting other people to change their behaviors to comply with your boundary. For example, if the boundary is to not interact with a particular person, then one sets a boundary by deciding not to see or engage with that person, and one enforces the boundary by politely declining invitations to events that include that person and by politely leaving the room if that person arrives unexpectedly. The boundary is thus respected without requiring the assistance or cooperation of any other people. Setting a boundary is different from making a request. Setting a boundary is also different from issuing an ultimatum.

The concept of boundaries has been widely adopted by the counseling profession. Universal applicability of the concept has been questioned.

A boundary is a rule that affects the behavior of the person who choose to make the rule. The point of a boundary is to control one's own reaction, rather than controlling other people's behavior.

Author and therapist K. C. Davis says "boundaries are an internal understanding of where I end and where you begin. It’s where my feelings end and your feelings begin. It’s where my ability to affect my own decisions and actions end, and your decisions and actions begin."

Setting boundaries does not always require telling anyone what the boundary is or what the consequences are for transgressing it. For example, if a person decides to leave an unwanted discussion, that person may give an unrelated excuse, such as claiming that it is time to do something else, rather than saying that the subject must not be mentioned.

Setting and enforcing boundaries is usually emotionally uncomfortable and requires effort from the person setting the boundary.

Co-Dependents Anonymous recommends setting limits on what members will do to and for people and on what members will allow people to do to and for them, as part of their efforts to establish autonomy from being controlled by other people's thoughts, feelings and problems.

The National Alliance on Mental Illness tells its members that establishing and maintaining values and boundaries will improve the sense of security, stability, predictability and order, in a family even when some members of the family resist. NAMI contends that boundaries encourage a more relaxed, nonjudgmental atmosphere and that the presence of boundaries need not conflict with the need for maintaining an understanding atmosphere.