And yet the nerve impulses which caused the muscles in your arm to contract left your brain about 500ms before you became aware of deciding to raise your arm. (http://www.ncbi.nlm.nih.gov/pubmed/6640273) Additionally, the mechanisms which sent that nerve impulse were spinning up for up to 10s before that (http://www.nature.com/neuro/journal/v11/n5/abs/nn.2112.html).

The you that lifts your arm and the you which feels like it decided to lift your arm are on different schedules.