You cannot negotiate break up. You could be civil and considerate leaving the person but there is nothing to negotiate. The only time you’d need negotiation if you have children and custody concerns, shared property, legal entanglements, mutual finances etc those need to be negotiated. In other cases there is nothing to negotiate. The other person doesn’t need to give consent to you leaving. Remain polite by informing the person that you need to end a relationship. He can’t make you keep dating him. Break up isn’t something you can negotiate. It would just prolong the break up and will be a waste of time if you want to end it.