There are 2 kinds of awareness regarding your speaking that relate here: One is being aware of words, attitudes and inflections that give mixed messages to the listener (the subject of the link I’ve included below).
The second kind of awareness is hearing yourself so you can stop undermining your credibility. Being aware of what you’re saying and doing requires serious focus and is worth working on. One of the ways to work on it is mentioned in this article–find a friend who will let you know when you slip. Conquering both kinds of awareness help you to be invisible–that place where people hear your ideas and look for your flaws.
Getting these wrong can indeed sabotage your career.
http://www.everydayhealth.com/womens-health/crimes-of-conversation-how-your-speech-is-sabotaging-your-career.aspx?xid=aol_eh-gen_2_20120423_&aolcat=HLT&ncid=webmail8