The "heaven" mentioned here has no mysterious meaning, but is outside our nature. Although everything in nature is unpredictable, it actually has its own internal operating rules, which are objective and independent of people's subjective will, which we human beings can recognize.
As long as we strictly follow the laws of nature, we can achieve advantages and avoid disadvantages, and turn adversity into prosperity; If you violate the laws of nature, you will be punished by nature.
Extended meaning:
On the question of which comes first, man and nature, China's philosophy is similar to that of western philosophy. Western philosophy does not deny that man comes from nature and that man is the product of natural development, but there are differences between Chinese and western philosophy in their attitude towards nature and man's position in nature.
Western philosophy advocates that nature is an objective existence without life, that man is the measure of all things, that man is the master of nature, and that man's purpose is to conquer and defeat nature. This is a typical anthropocentric view and the inevitable result of the dichotomy between man and nature in western philosophy.