"NO" is a word that must never be negotiated, because the person who cooses not to hear it is trying to control you [...] Declining to hear "no" is a signal that someone is either seeking control or refuses to relinquish it" —Gavin De Becker
We've spent a lot of time over the last year and a half thinking carefully about physical boundaries: we rapidly became adept at leaving two metres between us and the person walking down the street. But boundaries aren't only about physical distance or for people we don't know.
You are allowed to say no. You decide when you are uncomfortable and have had enough.
If someone is not listening to that, it's a huge red flag, whether it's someone you don't know or in the context of a relationship.
You don't owe strangers an explanation or justification to say no.
Quote is from Gavin De Becker's book The Gift Of Fear, recommended reading!