It's important to identify your values in combination with your boundary work.
Why? Because it's important to know your "why". Why is the boundary important to you? What values are you honoring by setting this boundary? If you don't hold this boundary, what values are you allowing to be trampled?
Values are either fear based or conscious based. If a boundary is set because of a fear based value, the follow through will have the same fear attached. Making it difficult to hold the boundary. Which is where most people feel stuck or they feel the boundary simply "didn't work". Fear based value boundaries can cause power over or power under responses.
Power over would be trying to "make" someone do what you want and is really more an ultimatum than a boundary- "You do this, or else...". The truth is, people have a choice in responding to your boundaries. You don't have the power to "make" an adult do anything. You can however, make a request and take the necessary actions for yourself if the other person doesn't respect a boundary you've clearly set.
In the case of power under, you may not speak up or may not even try to set a boundary because of fear of the other person's response. You may feel afraid the other person will feel angry- which is a very real possibility. When you start valuing yourself and setting boundaries, there may very well be backlash. People don't like change. It doesn't mean you shouldn't honor your values with boundaries. It takes practice. It's like building a muscle. You don't walk in the gym and go straight for the heaviest weight they have. Start with something small and build on that success. Small, consistent actions build trust in yourself.
The goal is to own your power in a balanced way. Getting clear on your values is the first step in creating boundaries in alignment with who you are. You get to decide who that is. When you are firm on who you are, holding the boundary becomes much easier.