Fun fact, the idea of becoming a genius by using 100% of your brain is retarded for even bigger reasons that extend beyond all the typical reasons mentioned in this video; important aspects of brain chemistry can only be activated when sections of the brain dampen in activity, causing other parts to increase in activity.
The most popular example of this entails the temporal lobes in which, using either transcranial magnetic stimulation or transcranial direct-current stimulation, by dampening activity in the left temporal lobe, the right temporal lobe will pick up the slack and make the person subjected to the treatment more creative.
The most important example, however more obscure, involves activating a person's flow state by dampening activity in the dorsolateral prefrontal cortex, which will inversely increase activity in the medial prefrontal cortex, triggering an artificial flow state. This is called transient hypofrontality. This is important to note because inducing transient hypofrontality has been documented to increase learning by up to 230%.