If you have problems establishing your boundaries, you actually have problem expressing your anger. As the purpose of anger is to create safety by making you defend your boundaries. It is the energy that fulls you to do that.
Boundaries have two main characteristics they are nonnegotiable and unalterable.
In order to be enforced, the other person either respects them or the relationship ends. There is no in between when or compromises when it comes to boundaries.
This are things that absolutely need to be respected in order for you to be treated fairly, or have a chance to be happy.
Like the borders of a countries, if you want to enter that country and you don't meet the requirements you are not getting in no matter what do you do. If you try to enter with force in some cases you are going to get killed.
If the person in charge of defending the border becomes corrupted and lets people in by accepting bribes. The entire community is going to suffer the negative consequences of the people that got in and shouldn't. Assuming the value of the community by which they chose to keep certain people out are not corrupted, as far as I know psychopaths can have very strong boundaries.
Look at countries like North Korea, they are very selective with the people that they let in to visit not because they are bad people but because they want to protect the dictatorship. Just because someone has strong boundaries it doesn't mean it is a good person.
So it is also important to chose your boundaries wisely, based on virtues and higher values than yourself, this is why self knowledge is important.
People who have low capacity to defend their boundaries in their relationships, are like corrupt border guards. Only that instead of money they ultimately accept as bribes a couple more minutes of not felling their anxiety, and then they suffer the negative consequences of bad people that shouldn't be in their life anymore. Instead of the end of civilization that happens when a country has no more boundaries, you will experience the end of your happiness and the end of your love towards that person.
In order to have a bond with someone you need two things, some sort of value that it is relevant for the other person and boundaries, rules under which you agree to share your value with that other person in a way that is fair for you. If someone walks all over you not only that person is not loving you now and it doesn't have any respect for you but that person never loved or respected you to begin with.
Behind your anxiety there is rage, the energy that it is making you run away right now can also make you strong and move you in to action, if you ever chose to externalize it.
