Human character is like a land. The soil is loose, there is a clay, there are many foods that grow plants, and there is a lot of water absorb.
So it is with humans. Humans are stingy, some are generous, some are liars and various other characters.
If you know the character of the land, you will understand how to walk on the land. For example, the slippery ground, you have to walk slowly and carefully. The ground is hard, you can walk casually as usual.
Likewise with humans, if you understand the nature and character, you will know how to deal with that man.
Every first encounter with humans will reflect 70% who he is. So, whenever anyone met, it was as if it were the first and last encounter.