The heart..
One interact with the world through the heart..
If the heart is hardened and cold, the world will feel him hardened and cold..
If the heart is soft and relax, the world will feel his friendliness and kindness..
If the heart is evil and cunning, the world will seek revenge at him on his work..
If you want to give and receive the world with values, then guard your heart more than anything else, because the source of your life flows from it.