Your values/behaviours are given to you via both your genes and your environment - which are effectively random. If your parents were prone to addictive behaviour in an environment that provides addictive substances - you will probably do the same.
This reminds me of thing I've always found highly curious about how the religious think.
They can't seem to understand that their choice in religion is relatively arbitrary and geographically dependent. Born in America you're Christian. Born in Pakistan now you're Muslim. Born in India now you're Hindu. Born in Israel now you're Jewish.
The fact that people can't seem to understand that the reason they believe in X god instead of Y is merely a question of a few hundred miles.
Life is particularly arbitrary. For example: I'm an atheist because of my environment (middle-class male, western country, studies science and technology, with access to freedom of speech). This is irrelevant as to whether atheism is actually the right option (which I believe it is - but then of course I would :) - the key fact to understand here is how the environment determined it.
Finally, physics eliminates the case for free will. So yes - you do what you do because you were set up to do it.
We're all just biological machines.