Heaven signifies night and day, cold and heat, times and seasons.
The world is made up of opposing pairs, yin and yang. Seeing and understanding these can give you advantage, for example understanding the real impact of high and low ground, or fighting in summer or winter. This is embedded in the contrast principle.
Heaven is the opposite of the hard earth, indicating light, rain, temperature and so on.
In business, when you are doing well, know that doing badly is never far away. If you have enemies then you may also have friends. Do not be trapped by single-track thinking.