the environment around you...think about it....when you smile and are happy, you elicit smiles even from strangers and create an aura of well-being around you. Likewise, when you are fearful or angry or upset, the vibes that emanate from you create an atmosphere where those around you say things they did not mean or believe in, get tied up in their thoughts so that the words come out all wrong and there is a general air of discomfort....
Maybe that's why wise men have said that even if you are feeling dreadful, keep a smile on your face....it'll help you and allow others to help you too...