I think that "fate" is a question of definition. But if you consider that your choices are made under influence of your genes (your genetical backround) and environment (situations which happens to you or, experiences), this "fate" becomes quite a possible. Because you decide according to your genetical backround (what is natural to you) and according to your experiences (environment). So, I think, in this case word "fate" doesn´t sound so mystical :)
Sometimes I feel like fate has been decided for us because things just happen. Other times you are given an option. You may choose the right option or the wrong. Everyone hits the fork on the road. It's not the fact that I believe in god. I don't. The reason is everything keeps moving and in order to do that fate is chosen by the universe.
First of all, the notion of "fate" is silly, since there's no way to falsify such a theory (until time travel is invented or we find a way to go to parallel universes). So even if such a thing did exist, you'd never know for sure anyway.
Onto why we decide our own fate. Firstly, we make hundreds of decisions every day, from the simple ones like when to get up, to more important ones like what car to buy. There are many variables that influence most, if not all those decisions. To imagine that there's some force that can not only move all those variables in a perfect way to make you do what you were "meant" to, while keeping everyone else in line with it's unknown plan is a little too far fetched for me to take seriously
As my headline suggests, we can all considers competing factors and conclude one out of many different alternatives. This ability to do so hints that almost every animal reacts to impulses or thoughts, given a set of circumstances.
If something as overarching as pre-destined fate of all life would've been present, then there would be little need for us to even think otherwise. There wouldn't be any advantage - evolutionary or cosmic - to be unable to change our minds or define any action as "the better" one. One could object that whatever will happen, is the only way it will happen. But I figure if fate would've been pre-destined since the Big Bang, then what need do we humans even have for a complex brain that constantly battles with itself.
It's clear that our choices are influenced. What's not clear is the extent. Since we are limited in our ability to make observations and inferences we can never for sure whether we even have free will. It's not something we can figure out. But generally it's best to believe that we do have free will. People who don't believe in free will have been found to behave more irresponsibly, even antisocially (as in being a jerk not being shy).