This doesn't say that we are predetermined to do something, simply that we are prone to conservative thoughts and actions. Which is another survival mechanism imo. This however could be used to argue that instincts and hardcoded behaviour has a deep impact on the concept of freedom of choice.. but it doesn't negate free will.
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It isn't possible to determine if we have free will or everything is pre-determined, short of the divine being appearing at noon in Times Square to buy everyone a cappuccino and explain it all.
Schopenhauer isn't barracking for one side or the other in this text, which is why I quoted it: he is just highlighting the delicious irony of our befuddled attempts to divine the ineffable.
This is why, when done correctly, a plot that included an argument about free-will versus predestination can be a terrific enema for the brain, like Twelve Monkeys for example.