If you set a boundary and someone else is disappointed or angry or upset, that reaction does not mean you’re not allowed to set boundaries or that it was wrong of you to do that.
If you ask someone for something and they say no, that does not mean you shouldn’t ask for things or that it was wrong of you to ask. Saying no to something, even if you really want it, is not (by itself) an attack on you, either.
There will be times in every good relationship where one person says no to what the other person wants. And there will be times when that answer feels bad to the other person.
That can be uncomfortable, but it’s healthy and good to be able to say no to each other. It’s healthy and good to ask each other for things and give the other person the chance to say yes or no. It’s healthy and good for each of you to be able to hear “no” and accept it even when it’s disappointing.
It’s healthy and good to own your emotional reaction and make sure you both agree that being upset is a normal and manageable feeling, not a crisis that requires someone to give up their boundaries.