Can you imagine action without reaction.
Action is pleasant; the misery is the reaction.
A child putting its hand in fire; that is pleasure; but when the body reacts, then comes the pain of burning. When we can stop that reaction, then we have nothing to fear. This child is godly, pure, innocent, harmless and always firgiving. The moment of truth dawns upon the child when its hand starts burning; that is the knowledge and this knowledge make it to react.
If it had not burned there is no reaction; no knowing of pain and therefore there is no fear. So making sure we understand what our action is all about, then it is easy to stop the reaction.