If the brain is a wetware computer that controls the flow of electricity like any other computer, how can you say you govern the behavior of those networks? Where's the demon that opens the gate that lets one thought emerge over another? You make a firm decision, but you arrived there through a chain of processes that began at the instant of the big bang (possibly before). So your environment, all instances and occurrences, were kicked off at some point, ultimately ending in you choosing chocolate over vanilla, but the "you" that arrived at that point is the product of variables all of which you, and everyone else, has had no control over. You can't break that long chain of causality and do something outside of the firing of your neurons, and you have no control over that.
You could say "I got drunk and changed the firing pattern." But really, the decision to get drunk was made by that same pattern, inexorably linked to the first photon zipping around a closed system.