Two things: 1. Considering we can't even predict which slit a photon will go through in a double-slit experiment or a stochastic system like the precession of a top spinning, it's difficult to say that our actions, each of which the results of many millions of synapsis firing in concert, are predetermined.

2. The complex series of algorithms including personality and prior experience are who you are. Furthermore, they're fully under your review, so if you don't like them, you can change them. You also have the ability to change your environment, i.e. inputs. So saying that our responses to stimuli are predetermined can only be true in the sense that you yourself have predetermined them.

Even if we were able to create a complete replica of our brains to the synapse level, that model would not be able to predict our future responses 100% because synapses are always changing. So who you are 2 minutes from now is not the same as who you are now.

All this to say that the belief that we have no control over the cause and effect in our lives is facetious at best and cowardly at worst.