Experts in the field of communication often quote the 55/38/7 “rule”.
The "rule" states people derive only about 7% of the meaning of a communication from the words themselves which the speaker uses (verbalized emotion), about 38% is based on tone of voice, and 55% from the speaker’s image and body language.”
The next time you are in a situation which involves speaking with your boss or potential clients remember the importance of body language and tonality. Image is also incredibly imortant especially when you're aiming to make an impression.
Simply keep in mind the numbers 55/38/7 and watch your approach in these situations improve.