Sensitive people should be treasured. They love deeply & think deeply about life. They are loyal, honest & true. The simple things sometimes mean the most to them. They don't need to change or harden. Their purity makes them who they are.
The only way to stop them is to cut them out of the equation of your life. It can make the narcissist angry. That evil narc is beneath the level of contempt. Void of understanding and empathy. They just don't care who they step on and hurt in the process.