There are two very famous sayings which can elaborate the question easily: 1.
First impression is the last impression...
Whatever you'll leave in first impression will last long till the last sentence of your business or life relationship.
2.
Your words are the mirror of your personality or the organization you are representing.
However you'll start the conversation, will effect the remaining body of your discussion, and however you're discussion was, will be effected till the last communication you'll have with that person or the client.