I don't think I have ever seen this posted before. If it has been, I apologize. I first read this in "The Sociopath Next Door." I wish I had read this three years ago. I wasted a lot of time and valuable gifts on a liar.
"Make the Rule of Threes your personal policy.
One lie, one broken promise, or a single neglected responsibility may be a misunderstanding instead.
Two may involve a serious mistake.
But three lies says you're dealing with a liar, and deceit is the linchpin of conscienceless behavior. Cut your losses and get out as soon as you can. Leaving, though it may be hard, will be easier now than later, and less costly.
Do not give your money, your work, your secrets, or your affection to a three-timer. Your valuable gifts will be wasted."