Boundaries are the Foundation of Self-Care
Identifying and creating boundaries is a true act of self-love, and it will help you to establish what is acceptable and what is not within all your relationships. For example, do you know what you are willing to tolerate or not from others? What actions or words from others cross the line for you? Becoming aware of your limits will help you begin to understand when people have gone too far.

Communicating your boundaries will help others know what you are willing to tolerate and what you can manage. For instance, I might share with someone that I am unwilling to work on Saturdays, because that is my self-care day, or I might communicate my feelings to a loved one who has said something hurtful. By communicating your boundaries explicitly, there is no mystery, and others are more likely to honour them, and you. Also, this practice helps others to learn how to set boundaries for themselves, and this will likely lead to healthier connections overall.
When someone violates a boundary (whether intentional or not) you will need to be prepared to honour the boundaries you have set for yourself. By deciding your boundaries ahead of time, you can decide what happens when they are crossed. An example might be deciding not to spend as much time with a friend who mistreats the time boundaries (consistently runs late) in the friendship. I would encourage you to avoid any passive-aggressive behaviours here as this would not be in line with supporting healthy connection with others. It can be tempting to want to treat others the way they treat you (like purposefully running late when you are meeting with a late friend) but that will not actually support your boundaries or your own self-respect. It is crucial that you share the impact boundary violations have on you with the person who has crossed your boundaries (as long as they are safe) so that a new norm can be established within the relationship. We teach people what we will tolerate.
Following through with your response to boundary violations may be difficult, but it is crucial in your quest to live an empowered life. By following through with your plan, you are honouring you, your boundaries, and your autonomy, and all of these steps will reinforce a strong self-care practice.
Take care of you and begin to establish a healthy self-care practice, founded on healthy and supportive boundaries. You are worthy of healing and healthy connection.