Expressing your needs and expectations requires practice. No one. I mean no one gets it right the first time. Practice makes progress.
I encourage you to practice your boundary statements in front of a mirror or with a trusted friend or ally. You can even write them out or have them close when you do express it to someone.
Expect resistance from others when you state a need that differs from the way you all used to be in relationship. It is absolutely part of boundary setting. People will make it difficult. People will express resistance. Change is hard. Change can be difficult for all concerned. This doesn’t mean you stop setting boundaries. When your need for boundaries is met with a resistance it is often a good sign that the boundary was needed and could help or strengthen the relationship.
Be open and respectful of other people’s boundaries as well. Part of healthy boundary setting is being able to honor and respect when someone expresses a need.