If you drive in Lapland and see ghostly pair of glowing antlers on the road, they're probably attached to a whole animal and you should start slowing down.
Sometimes the most important thing you can do for someone is to accept them for who they are. Accept their faults, their failings. Accept that they may never get better, or change, or be who you want them to be. But be there for them. Support them when they stumble, help them up when they fall. They may give you nothing in return, but they may also give you everything, show you things you never would have imagined, because odds are, you need the same things they do.