Are there any leftist organizations in your area? I guarantee you you're not alone in the way you feel, and if you start organizing with other principled and disciplined people, you can do something about it.

Edited to add: There's nothing inherently wrong with the other suggestions here; it's good to have tactics to manage your own mental health in the world we live in. But, at the end of the day, taking care of yourself isn't going to actually stop the genocide, or any of the other problems you mentioned here.

One of my favorite quotes is from Angela Davis, and it goes, "I am no longer accepting the things I cannot change, I am changing the things I cannot accept." I can accept that there are some things I can't change right now, but that doesn't mean that I accept them as immutable facts of life, or that I have to accept them on a moral level. Fixing society's problems is going to take a lot of time and effort, but that doesn't mean we should throw our hands in the air and give up, it means we need to get to work. And right now, not enough people are actually doing something.

I know lots of progressive people who are frustrated with the state of the world, but they stay at home and binge-watch TV because they think there's nothing they can do about it. Imagine the frightening progress we could make if every one of those people stood up and started organizing. Defeatism is the cancer that prevents the modern left from getting anywhere. People have to stop believing they're powerless if we want to get off the ground. Evil triumphs when good people do nothing, and I'm not going to stand by and watch the world burn. I'm going to grab a fire hose, but I'm going to need some help to actually put out the fire.