I was watching the movie Minority Report and in that Tom Cruise sees himself in the future murdering someone. In other words, his destiny was laid in front of him through precognition. Exactly at the moment that he was supposed to murder, the oracle who predicts the future was standing next to Tom Cruise and telling him that he has the free will and choice to alter the course of action. The oracle was constantly reminding him of his free will and that he does not have to be forced by destiny to do what he is supposed to do. As fate be, Tom Cruise was forced due to his anger to kill the person. Inspite of repeated requests by the oracle to use the power of choice, Tom Cruise subdues to the forces of nature and destiny.
Our life is also like the story of Tom Cruise in the movie. In reality, all the events in our life are pre-destined by the forces of nature acting through the laws of karma. Nature is so powerful that it incites the appropriate emotions and intelligence in our heart at the appropriate time so that we act as per our predestination and fulfill our karmic responsibilities. So if everything is predestined and based on karma, then why bother you ask? Actually, as per the oracle in the movie, we do have the power of free-will and that we do have the capacity to over-turn the predestined events that are supposed to happen. But because karma and nature is so powerful that to change our destiny using our free will on our own is like an ant wishing to move a mountain. It is not possible. In comparison to nature and natural laws of karma, our ability to control our intelligence and emotions is practically nill. Therefore, Sri Krishna says that surrendering unto Him is the only possible way to erase our predestination and pave a new future for ourselves.
The only person who is more powerful than nature is God Himself who created that nature and its concomitant laws. In the Bhagavad Gita, Krishna (God) reveals this truth that material nature is under His control and to overcome it is very difficult. Therefore Krishna declares that if you want to benefit yourself, simply surrender unto Me (Krishna) and I (Krishna) will take care of everything.
So what do we do with our free will you ask? We do exactly that, at every moment we must train ourselves to use our free will to depend on Krishna and not depend on our own capabilities of problem solving. The more we become an expert in depending on Krishna for all aspects of life, the more we will be released from our own karmic predestination.
This is the only way by which the power of free will can overcome the forces of nature (including predestination)