I don't think that's true. It appears to me that I could easily have made different choices. Further, it's an unfalsifiable premise; we can not determine whether we could, or could not, have chosen differently at any point in time, so any firm belief one way or the other is a faith-based belief.
Why do you think that we could not have made a different choice?
Yeah, it probably appears intuitively like that to most of the people around, and it did for me too for a long time. Personally, I'm way more impressed and convinced by the idea and data that all of our actions have a cause, or rather long intervening chains of different causes, than the idea that we could somehow break the chain of causes that demonstrably guide our feelings and actions.
I'm not trying to dodge the question, my answer continues below, but where do you think your particular decision comes from if not from previous causes and experiences? Could you give me the simplest example of a case where you feel that you could've chosen otherwise? I would like to discuss this in order to challenge my own thinking about this, maybe you too would get something out of it.
To continue my answer, in brief, if we accept that we live in a natural world where things are causally connected, there seems to be no way out of the chain-game. The other explanation (contra-causal free will) would require the breaking of the causal chain. It is also important to understand that truly random causes (the quantum of the gaps argument of free will) for our actions does not help the case for free will - in those situations the relevant actions would just be random. Anyways, my understanding is that those effects are very weak / non-existent in our everyday life, certainly they are very weak compared to the multitude of concrete causes that we can track down ourselves, everything "from blinks to winks". Contra-causal free will would mean that we could somehow break the causal "chains" (or random "chains") of everything that happens in and around us. I haven't seen any good evidence or solid reasoning to support this view.
On the other hand, I've seen much good evidence and solid reasoning that points to the naturalistic conclusion. For example various priming studies in psychology that actually show how the actions of the subjects are predicted and changed with good accuracy without the subjects ever being conscious of the real influences that guided their actions. Or the neurological studies that show how our decisions are made before we are actually aware of making them.
I just bumped into this post at Jerry Coyne's blog when I was looking for something recent to reference you about those kind of studies:
http://whyevolutionistrue.wordpress.com/2010/07/28/the-free-will-experiment/
And, you're probably already familiar with some of the priming studies:
http://en.wikipedia.org/wiki/Priming_(psychology)#Priming_In_Daily_Life
Or what about how different hormones such as oxytocin affect some of our most valued behaviours:
http://en.wikipedia.org/wiki/Oxytocin#Actions_within_the_brain
Female rats given oxytocin antagonists after giving birth do not exhibit typical maternal behavior.[39] By contrast, virgin female sheep show maternal behavior towards foreign lambs upon cerebrospinal fluid infusion of oxytocin, which they would not do otherwise.[40]
Are you familiar with the
www.naturalism.org site that I linked a few posts back? I find it a great resource on all things free will.