When we are tolerating behavior we don't like, it can be because there is a boundary problem. More often it is because we are hooking our feelings on other people's behavior.
For example, it is not a boundary to say, "No, I don't want to go out tonight." That's just saying what YOU are going to do. Saying "no" when someone asks you to do something is not a boundary. When we say "yes" to things we don't want to do, it is not poor boundaries, it is lying.
It is not a boundary to say, "I feel terrible because you don't do any work around the house." That is a guilt trip.
An emotional boundary is like a property boundary. It involves a boundary violation - someone coming into your space. For example, if someone hits you, that literally violates your personal space. If someone talks to you with a raised voice, that may be a boundary violation.
There are two possible steps in dealing with a boundary violation (sometimes you only need one):
1. Ask the person to stop.
2. Set a consequence to protect yourself.
The consequence you set is not to punish the other person. It is to protect you. For example, if someone is yelling at you at work, you could ask them to stop and tell them that if they don't stop, you will leave the room and report them to human resources.