anyone familiar with psychological quotes?

Hello,
I was reading online and a quote really stuck out. It says,
“Until we have met the monsters in ourselves, we keep trying to slay them in the outer world. And we find that we cannot. For all darkness in the world stems from darkness in the heart. And it is there that we must do our work”.
Any idea what it means?

?2018-10-28T15:28:50Z

When people hurt inside, its very common for them to strike out and hurt other people, hoping that will make them somehow feel better. For instance, it's common for someone who was bullied as a child to turn around and bully other people, thinking that now they are on top, they will feel better. But they don't. The only way they are ever going to feel better is to admit they are broken inside and get help to rid themselves of that "darkness".

Anonymous2018-10-26T22:26:01Z

I have trouble with that philosophy because its seems everybody has done just that. Nobody tries to slay any monsters so, they just let the big monsters get away with murder and act like petty monsters themselves.
But, there is a quote saying you see the world as you are.
In my case, I spent my first 30 years trusting and believing in people and always getting screwed.
So now that I don't trust people, that means Im untrustworthy?
The second quote, look up shadowwork.