means that you are weak and can't just think what you want. no one in this world is trustworthy. Trusting someone is pretty much telling them that they can do whatever they want and you will not question them.
GUY: "Babe, you don't trust me?"
GIRL: "Yes I do. I trust you with all of my heart."
Now he can cheat on her and keep saying "you trust me, i wouldn't do that to you."