Perhaps this video will put things in perspective. The other commenter is right, availability bias is at play. But just because we've gone far doesn't mean we should stop, and continuing to raise our standards of what is acceptable is a good thing. My belief is that a great deal of violence is caused by political, economic, and social deprivation and inequality, so if you want to feel like you're working against violence I would recommend working to reduce those. But that's my personal way of dealing with badness in the world. I don't feel totally powerless, I can't personally stop it but I can be part of a collective effort to mitigate it. I haven't done much research into the effective altruism community as I'm a poor college student with high future income potential if things go right, so I figure that landscape could change considerably.

The past is the past, but you are not powerless to stop bad things from happening in the future, it won't be you alone and it won't be clear cut, but you can definitely make the world a better place.