Human beings are a unique creation in the cosmic scheme of things. Unlike the untold billions of other life forms teaming on the Earth -- whose nature is an open and shut case -- human nature is not fixed. What does this mean to you? Only everything!
The tiger, the horse, and the bird must express their nature. They have no real choice. And even though they may be free to choose which part of the jungle, or open range, in which they want to feed and roam, these animals have no choice as to the kind of world in which they must dwell.
The tiger can't choose to live above the jungle floor any more than a shark can decide to soar through blue skies. The tiger, horse, bird, and shark must live where they do because of what they are. Try to see this deeply.
The tiger's nature determines its life. And that life is a part of the jungle floor. They are inseparable. The tiger's nature and its life level are one thing. The tiger's life level determines the world it must inhabit. Its nature and life level are as fixed as its stripes.