When an interchange between individuals starts, the tone of the conversation has a lot to do with the predictability of the outcome. If the first person to speak is courteous, the positivity of the discussion is much more likely to result in an outcome that is acceptable to both.
Many meetings are to deal with situations that somehow need to be fixed. If you expect that the other party will upset you, the likelihood that they will is increased. If you accept that they will cooperate, the likelihood they will is increased. You can influence outcomes by expecting pleasant people and positive outcomes. It is well worth the effort as sometimes unforeseen benefits can also happen as well as friendships that may last many years.