Why do bad things happen to good people?

I think bad things happen to good people bcuz the devil want to break down the strong. I also think bad things happen to good people bcuz maybe God just wants it to happen. And also good people sinned and they might of not told God to forgive them. 

Genesis 4:7 

⁷ If you do what is right, will you not be accepted? But if you do not do what is right, sin is crouching at your door; it desires to have you, but you must rule over it.”