Do you believe in mental abilities? Do you have any?

This reminds me of the Rain Man.

Is he mentally disabled or is he mentally enhanced?

The ability to remember everything but being a bit slow...

If we could fully use our brain we could be unstoppable.

Thing is, that's precisely why we can't.

Somewhat lossy, but efficient, versus highly detailed and exact, but inefficient overall.

In some ways, it's like image compression:

 Example

Here's Vathek's image rendered as a PNG (it was originally a JPG, so it's really still only JPG quality... bad example, oh well)

 211 KB

It retains every last pixel, but consumes a lot of space doing so.

And as a JPG, at 80/100 quality according to Paint.net

 14.3 KB

Notice that there's very little quality loss, but much space is saved.

And just for fun, here's 20/100 quality.

 5.74 KB

And now you see how the space tradeoff isn't worth it anymore.

(You can tell I did this more as an excuse to screw around with JPGs than to actually illustrate my point but anyways.)

There has to be a trade-off between quality and efficiency. If the brain operates at higher quality in a certain area, it's less efficient overall.