Because there is something much bigger in this world that our flesh cannot comprehend.

But the mind isn't made solely from flesh.
The man follows the earth, the earth follows the sky, the sky follows Dao.
When celestial bodies move in the sky, they make waves. These waves reach everything on Earth. Earth shapes itself in accordance with the movement of the sky.
To catch what it tasty and avoid what is painful, the mind builds a model of Earth. The man shapes the mind in accordance with the movement of the Earth.
The brain with its flesh, is merely a library that stores the past. To compare it with the present. To know when anything changes. To see if there is anything to experience.
Dao, is the principle that allows all things to move.
The mind, its every thought, is shaped by Earth, shaped by the sky, shaped by the past, in accordance with Dao.
Does it really matter how much flesh we claim to have, when every thought is formed under the combined effort of everything in the universe?

If we follow HIS will and become living sacrafices we can bring the Kingdom onto Earth.

Our mind, they say, is born full and perfectly at peace. And only when we use the mind to nourish our favorite worldly distractions, it is depleted and become incomplete. And we make ourselves suffer.
By rejecting all worldly temptation, which can be achieved only after understanding their true nature, one can make the mind full again and experience true peace.
And see the heavens. Which have always been here, hidden in the heart.
This doesn't explain who is this HE. And why should I follow his will.

Right now, the US is 'Do thou what you wilt."

The mind loves presenting itself as the absolute of rationality and the true cause of all our actions. But in practice, people rarely do what they believe is right.
The mind has no power, it can only follow the heart. A mind that rebels against the natural order will only damage itself in confusion.
To change the future, you have to accept the reality. In the end, we can only do what we are willing to do. Only the personally experienced truth can free you.