In the heat of the moment, it's easy to give up right away because it's super uncomfortable. There is a lot of advice about salary negotiation online but it's all basically useless because most people just give up right away and reveal the number they had in mind, which is almost always below market, so they accept it. Just try to set a personal goal before the call and try your best to stick with it. The standard strategy is to be firm but flexible with the number you give, don't undercut yourself, and try to set the stage for another round of negotiations after a formal offer is made.