I posted this article in an early blog post, but came across this paragraph again. This is a great explanation of boundaries. Click below for the whole article.
Set the boundaries with grace and love and leave it to the toxic person to decide which side of that boundary they want to stand on. Boundaries aren’t about spite or manipulation and they don’t have to be about ending the relationship. They are something drawn in strength and courage to let people see with great clarity where the doorway is to you. If the relationship ends, it’s not because of your lack of love or loyalty, but because the toxic person chose not to treat you in the way you deserve. Their choice.