Using positive words or expressions in the business writing will convey goodwill and willingness to serve the customers. Negative terms will imply criticism. Nobody likes them. Consider the following sentences:
Negative: You didn’t mention the size you want.
Positive: We will be appreciated if you let us know the size you want.
The first sentence indicates that the customer did something wrongly. On the other hand, the customer is being criticized. Meanwhile, the second sentence will convey positive meaning. The pronoun “we”, and the word “appreciate” are a personal term and positive word, respectively.