You are what you do, not what you say you'll do. - C.G. JungIt's been said that anxiety and nervousness are reduced in public speaking when we do so as a form of service has broad implications for perhaps all of our interactions.
Throughout my career, I've shied away from an explicit role in "sales". Sales isn't "good" or "bad" - I just never thought of myself as a salesman. Yet so many people with whom I've worked have told me, repeatedly, that I'm a natural, and that I'm incredibly effective at selling. I am, in fact, responsible for tens of millions of dollars worth of completed contracts and transactions, yet still don't think of myself as a salesman. I've pondered this over the years, and my epiphany on the subject seems obvious in retrospect, but took some time to understand and embrace.
If I have to present a topic that is of no interest to you, and might in fact be counter to your best interests, I will be uncomfortable. Succeeding would mean, in short, that I've fooled you. The best shysters might be perfectly comfortable with this, as they've developed confidence that they can close the deal regardless of objections. Even worse perhaps, they may be able to convince themselves that a sub-optimal deal actually IS in the best interests of their prospect.
In contrast to this, if I have no problem whatsoever enthusiastically sharing something with you when I am totally confident that it will benefit you, it doesn't feel like "sales" to me.
In the first instance, I am misleading you, and satisfying my own interests at the expense of yours. Anyone with a conscience would be uncomfortable. In the second, I can be confident that you'll be appreciative (at least in the long run), because what I'm describing actually benefits you -- any value I accrue comes in large part from your satisfaction. Far easier to feel comfortable delivering a message like this!
Public speaking is a variant of this idea. While it's recognized as one of the most common fears, I have found the anxiety dramatically easier to overcome when I started to see the difference in audience response when I have something to share that's of importance and value to them. If anything, I have to check myself to rein in boundless enthusiasm when I have something to share that I know will grab my audience's attention and appreciation.
Interpersonal transactions, whether one on one or from a podium to a large audience, engender far less anxiety when based on an honest service motive. Conversely, the most anxious moments come when we attempt to "sell" something disingenuously. A wonderful byproduct of this is that, rather than avoiding you, people will start to seek you out as they come to realize that you truly have their interests at heart.