Life is a series of causes and effects, and we're the ones tasked with the beautiful notion of wondering why.
Sometimes I like to think that life is a big chain of events where each condition in each moment is explicitly linked to the moment before, and thus the moment after. Each future moment relies on the one that came before, one that is so definite and exact that there can only be another definite, exact moment that follows. Sort of like there was (is?) a function right at the beginning of time that set up all of moments to come. And then sometimes I like to think I have a choice of what to think and how to act... but I'm not sure about that.
It's really interesting when you think about the beginning of the universe. How everything was so orderly in its chaos. And we're able to look back at it and describe it with math! From that chaos, though, came everything. Came you, came me, came the internet, came the neural pathways I'm using to control the muscle tissue in my fingers to type this! And I like to think that somehow we all maintain just a little bit of that chaos from the beginning of the universe. And because of that we can still determine our lives. That's what I like to think, at least.