To say no was to argue a no;
Nietzsche said:
“It is better to have a bad explanation than no explanation at all”.
Saying "that doesn't suit me" is a very difficult exercise for people who find it difficult to set limits. Note, however, that the most important thing is not so much the content of the argument as the fact of arguing.
To say that "it doesn't suit me" is to show others who you are . We are indeed defined from the limits that are ours.
To say no when something does not suit us is to say something of oneself. If, for example, confiding "I don't like red", it means that I don't have the same experience, the same feelings as others. And I just let it be known.
At the same time, it says better who we are and it allows others to better appreciate us or not to appreciate us, but the challenge is, as you have understood, to let people know who we are. .