When we learn to tend to other’s needs or we learn how to behave from observing other’s unhealthy boundaries in their relationships, it makes it hard to set our own boundaries. People who, are not use to hearing assertive boundary setting from you, may react negatively, which might provoke anxiety and guilt in you for asserting these boundaries.
It is important to realise that hearing boundaries and setting them is also new for others ,who do not except it nor are used to it ,thus give yourself time to practice. Give others time to adjust and to get use to your new behaviour and expectations. If others often react negatively to you, it might be time to recognize that the relationship may be unhealthy to you.
Your negative emotions are valid. You have a right to express them and make a requests. These emotions tell you that the fence has been crossed and that you do not like it.
Before you communicate, especially when it is new to you, take the time to deep breath and reduce the intensity of the emotion felt. Do something to help yourself get re-centred and focused. Once calmer, think of how you want to come across during the interaction and how you will communicate your concretely defined boundary to others.
In formulating your message avoid ‘’you’’ sentences (e.g. you make me so angry when…). That comes across as blaming. Instead use “I statements”: “I feel angry when xxxx happens… if the other reacts by arguing and throws accusations at you, then address that you do not appreciate that behaviour and that you stand by your request. When you feel negative emotions raise again walk away and focus on an activity that give your energy.
If the behaviour repeats its itself ,make it known that there are consequences for not respecting your boundaries. Think what are the costs that you are willing to accept and what not and communicate it clearly.
Try taking these steps and evaluate the results. Without trying to set up your fences and protect them, you will not take good care of yourself and you will not achieve healthy relationship ,which you deserve. Take a chance and evaluate what you think and how you can improve your communication in future situations.