Negotiating is not fighting
Pushing a bit more is not a fair negotiation technique.
Repeating an argument again for the fifth time will neither make it valid not the other person honestly buy it.
Conversation, negotiation and collaboration in teams, with partners, clients and stakeholders is not about winning or losing. If you just «win», be aware that you actually also lost. Because that winning was at the cost of not being able to have an agreement and sooner or later you will pay the price of that somehow.