It does not matter what you know; it especially doesn’t matter what you think you know. Life is ever-changing. The ability to change your mind instantaneously is not one that only superhero’s have. Anyone can say one thing and suddenly change their minds milliseconds later.
While you believe that you have things figured out or that you to know what to expect from that person before they are even aware of it themselves; free will enables that person to change their thoughts/actions. The beauty of free-will is also the thing that keeps your own free will caged. See, whether we want to admit it or not, “free will” is a relative term, because everything we say and do is dependent on the free will of another. We are all connected.
For example, my free will would allow me to decide go to a movie tomorrow night and you are the one who always drives me to the theater because I do not drive. Your free will is what makes you decide to go to a romantic dinner instead of taking me to the movies. See, your free will affected my free will.
Let’s throw in another variable and say that your decision to go to a romantic dinner affects my decision to go to a movie, but your boss’ free will helps her make the decision to have you work late that same night. So, my free will to decide to go to a movie was affected by your decision to not take me to a movie and instead go on a romantic date. Your own free will to go on a date was influenced by your boss’ free will to cause you to work late at the office and instead cancel your date.
What I am saying is that we may have the free will to do something, but everyone’s free will depends on another’s free will; and that consequently displays a person to have no free will at all. Each one of us is connected; whatever minor, seemingly insignificant thing someone else decides is going to affect you (even if it is not immediate)…get use to it.