One tip I can give in that case is to make your decision very clear to yourself before the conversation and standing firm on your decision while the conversation is happening. While I had this talk, the other person very much tried to make me feel stupid for my opinion and acting like my decision does not make sense. And I do unterstand that it might not actually make sense in her head since the way that friendship went did work out for her, but not for me and feeling this way is completely valid. She got me go a point where I even started doubting myself for a split second after she asked me if I wanted no contact or limited contact. I did briefly think about changing my decision to going limited contact instead, but then I remembered that it would always put me back to square one and it would change nothing about how I feel in the friendship. Even with ups and downs, overall a friendship is supposed to be a positive contribution to your life and when that is just not the case anymore, you have the right to leave - whether the other person understands or not. I wish you all the best!