There's no need to stop caring. And clearly you do care. What you need to do is stop feeling responsible for things you have no power over. Because that's what's stressing you out.

Change your perspective. Instead of focusing on the things that are wrong that you can't fix, focus on the things that you did fix, or that you have a good chance of fixing in the near future. They may be small things, but at least you can leave the world a little better you found it every day.