Be careful not to think that just because you know what a person is going to say, you know what that person is going to do.
Be careful not to think that just because you know what a person is going to do to others, you know what that person is going to do (or not do) to you.
These mistakes are made frequently by people, and I imagine they are often the last mistakes such people make in life. The ability to see yourself objectively, in the third person, is a key survival tactic, but most people cannot (or choose not) to do this. Such self-awareness is particularly useful when you find yourself making one, or both, of the mistakes described by these aphorisms. Simply having an intimate enough relationship with someone, such that you have an insight into their potential behavior in a given situation, does not make you invulnerable to that behavior. Simply knowing what a person is likely to say in response to something may not give you insight into what they are planning to do about it. The bottom line: When dealing with dangerous people, never think yourself immune to their actions simply because you may be able to predict how they will behave towards others. Do not take comfort in your understanding of such people. Place yourself in the position of a person who does not have such understanding, and get out while there’s still time. In this case, knowledge only gives the illusion of power.
Because I am beginning to make a habit of recommending films that depict the relevance of the aphorisms under discussion, my suggestion is to re-watch the film, Casino, with special attention paid to the character of Andy Stone (Alan King).