First off, to me there's a fundamental difference between fate and destiny, but I'll explain what I mean just now.
People are, for the most part, animals. They act and react out of instinct and based on their neurobiology, and then they tend to rationalise those instinctive acts later. Bigotry for example - it's instinct - we're a social animal, and for the security of the pack, we only tolerate difference up to a certain point before we attack it and drive it out. On the other end of the scale, psychopathy is a structural variation in the brain that makes people less sensitised to serotonin, amongst other things, and makes them less able to consider the consequences of their actions or to take the needs of the group into account.
So yeah, from that point of view we are all slaves to our nature. We may think we make decisions and choices, but ultimately it boils down to our biology reacting to its environment, our memes and genes doing their best to propagate. And because it's so predictable, it forms a pattern that can be read, predicted and manipulated. That is fate, simply the huge big pattern of cause and effect.
Except...
Make somebody who is psychopathic aware of what they are and then give them the tools to manage that condition - things like meditation and medication and anger management classes, and that person can change. As a subconscious, unknown trait it ruled that person's fate, but in becoming aware of it and learning about it, that person gains control over it and unravels that particular strand of his or her fate. I believe that the same is true for everything else that drives us - greed, bigotry, love, infatuation, compassion, even GID - especially GID. As long as we are unaware of it, it sits there eating at us, manipulating how we react, but the moment we become aware of and accept a driver, we take control of it, and we can guide circumstances to give ourselves a better fate.
But then of course there IS circumstance, and that to me is destiny. We don't all get the same opportunities to become more aware and less ignorant and so gain control of our fates. The fact that my mom chose to stay home and teach me to read at an early age gave me a love of reading and learning, which helped me become more aware of things. The same cannot be said of a child growing up in the Sudan today, who is too busy trying to figure out where her and her five siblings' next meal will come from. So from that point of view, I suppose we do have destiny, but within that destiny we can change our fates through knowledge and understanding.
As Pythagoras said: "Know thyself and thou shall know the Universe and God."
Mina.