On one hand, the predestination is a sure thing, both according to the bible and based on our understanding of the "now" concept of our cosmos. The ENTIRE history of cosmos (our past, present and future) is "NOW" to God, in full, instantaneous and simultaneous view of God. Thus, God predestines all events in our cosmos in this holistic sense.
On the other hand, the freewill choice of mankind "reveals" the superpositional mystery of God's predestination and man's response. That is the double-slit quantum experiment type of mystery. To say that God fixes our choice a priori is like saying that the photons can only pass through one of the double slits, not both at the same time. To say that our choice has nothing to do with God's predestination is like saying that the delayed choice has no bearing on the result of the double-slit experiment.
Our mind is able to handle either/or, but not either/or/and! We must learn to accept the mystery of the Schroedinger's Cat: the Cat can be both dead and alive at the same time! Our uncovering of the lid will reveal if the cat is either dead or alive!!
Arminianism does not underestimate God's sovereignty but emphasizes the usefulness of God's prevenient grace in enabling our freewill choice, whereas Calvinism overemphasizes God's sovereignty in the expense of human choice, which is really under the VERY sovereignty of God. I think both are not fully correct, they each get a piece of the puzzle.
God predestines that Soccerfun will each some types of food during the day. Soccerfun laid his eyes on Steak instead of Pork. That choice turned out to be God's choice too. That is the mystery. Did God fix soccerfun's choice beforehand? God would ask Soccerfun this question: So my child Soccerfun, what did you find my choice for you? Soccerfun would have to answer: Steak, not Pork. God said: well done, that is my choice too.
The next day, the same thing happened, except that Soccerfun chose Pork instead of Steak. Soccerfun tried to quiz God: Dear God, what was your choice for my meal today? God would answer by asking: What did you find out then? Soccerfun said: Pork this time, not Steak. God replied: well done, my child, that is exactly my choice for you.
On the third day, Soccerfun tries to test God before he makes up his mind: Dear God, what is your will for me for my next meal? God would answer, again, by asking a question: Dear child, what would you choose for your next meal? Soccerfun tries to be ambivalent: I have not made up my mind. God answers back: Well done then, wait until you make up your mind and I will tell you if your choice is mine too.
Soccerfun is baffled by God's indeterminate answer and asks: God, are you serious about your choice for my next meal? God would again answer by asking: But have you made up your mind now? Soccerfun replies: I am leaning toward Salad today. God says: well done then. Go find out once you make up your mind.
Soccerfun, all of a sudden, understands the dynamic relation between God's will and his choice.