When your partner is being what you consider to be unreasonable how do you decide to give in or hold your ground?

Your partner is pushing you to do something, and you’re really not up for it. Treat this completely as wide open as you want, because this could apply to so many situations. In my case I told my partner 5 times I didn’t want to do something. She insisted on trying to do it herself, and couldn’t do it and got pissed at me. God I feel like I’m in jr high. Your thoughts? As always humor greatly appreciated.