“Man is disturbed not by things, but by the views he takes of them.”
Iron is full of impurities that weaken it; through forging, it becomes steel and is transformed into a razor-sharp sword. Human beings develop in the same fashion.
As soon as you concern yourself with the ‘good’ and ‘bad’ of your fellows, you create an opening in your heart for maliciousness to enter. Testing, competing with, and criticising others weakens and defeats you.