I once told an employee, "If you can't negotiate for your own salary, what can I expect when you are negotiating on my behalf?"

If you want something, best have your data ready, feelings don't matter.
Best know what is possible, can't get blood from a turnip.
Better be willing to walk away from the deal if you put it on the table, idol threats will not help. If you suggest you will look elsewhere then they will replace you regardless of the outcome of the negotiation.