The myth that we only use 10% of our brain, turns out to be true. We spend 90% of our thoughts on useless crap, worry, etc., so 10% is the net result.
If we become mindful, and clean out our minds, then we can truly use its full capacity, and be much more intelligent. This is why we can perceive Truth much better if we are mindful.
Meditation is the key to Mindfulness is the key to Self-Realization is the key to Enlightenment.