This is a oft repeated question in philosophical discussions and we always have people taking the side of Free will or Destiny... But the best answer to this vexed question, according to me, is how H. H. Sri Sri Ravi Shankarji explains it.
He says and I quote, "When people consider the past as free will they are filled with remorse and regret. When they consider the future as destiny, lethargy and inertia set in. A wise person will consider the past as destiny and the future as free will. When you consider the past as destiny, no more questions are raised and the mind is at ease. And when you consider the future as free will you are filled with enthusiasm and dynamism. Of course there will be some uncertainty when you consider the future as free will, and some anxiety, but it can also bring alertness and creativity. Consider the past as destiny, the future as free will and the present moment as Divinity.
This is like the Last Word on this subject isn't it??