By LUPER 
The phrase “Helping a manipulative person is like giving the keys to your house to a thief” illustrates the idea that when you assist someone who manipulates others for their own benefit, you’re essentially giving them access to your personal boundaries, resources, or trust—much like handing over the keys to your house to a thief, allowing them to take advantage of you. A manipulative person may exploit your kindness or help without any intention of reciprocating or being genuine, often using the situation to serve their own selfish goals. By helping them, you risk being taken advantage of, just as you risk losing your possessions or security when a thief has access to your home.
