Pot calling the kettle black: People who retreat 50 steps in battle laugh at those who retreat 100 steps. Metaphor means that you have the same shortcomings and mistakes as others, only to a lesser extent, but you laugh at others without knowing it.
Complaining about others: Heaven: Destiny, Fate; You: Resentment, blame. It refers to complaining and blaming others blindly when encountering setbacks or problems.