There are always constraints and preferences and whatnot. Do you have time to pick up the can? Do you care about the garbage on the street? And this will result in an action be somehow combining all those bits and pieces. Could be perfectly deterministic but could as well have an element of randomness, for example you care enough to pick up the can four out of five times if no other constraints prevent you from doing so. But whether there is some deterministic logic behind your decision or whether your brain just flipped a coin or a combination of both, there is no deep mystery here, just a very complex system that is hard to predict.