advice is welcome!

How do I help someone who isn't willing to help themselves... you can't I know that but let me give you a quick story first. My SO is very stubborn and one sided. He only thinks one way, well recently he got hurt and now will have back problems forever. One day he complains about not being able to do anything, so I plan something and now he doesn't want to go. He has pain meds he should be taking daily but refuses to. We get into arguments about this all the time. I will never truly understand his pain but I understand when he says he needs to get out. I just need advice on how to empathize him and deal through it when things get tough. Again, any advice is welcome except rude comments.