No one chooses anything. Your decision is not a magical event within an inviolate soul. It's a physical process that obeys the laws of physics - those laws decide what you "decide", not you. Your "decision" is an electron migrating across a synapse in your brain. We could trace the path of that electron back to the first thing that happened. Along the way it wasn't affected by "you" in any way, because "you" does not exist - we do not actually have souls even if it's fun to think that we do. This is not determinism, it doesn't matter if there is (determinism-destroying) electron randomness, you still have no decision.
I hope this helps. And now, for your next response, which will be one of these two retarded statements:
1) We just don't know exactly how the brain works! There could be magic happening in our brains for all we know!
2) It doesn't matter anyway lol!