I often emphasize the importance of boundaries, but many people still don't know how to understand it. Actually, you can think of it as the cost for others to interact with you. For example: if someone borrows money from you, you can say no problem, but it might take some time, require paying certain interest, or going through a process—all of which are costs. Because human nature follows a rule: where the cost is low, people will gather there. People who lack a sense of boundaries are essentially infinitely lowering the cost for others to use or interact with them.