Knowing both people in the quotes above, I could see that neither of their comments were grounded on reality.

On the one hand, I know the first person to be someone who has a perception of himself far greater than his actual reputation, in many aspects of his life.

The second person is a very nice person who comes across very well in life.  She has a humble and sweet nature and would give a nice presentation if given in her natural manner.

Both people’s feelings clearly come from outside of the reality spectrum. 

Somewhere in the middle, your nerves come into the reality sphere where you are nervous for good reason…. Maybe you are unprepared or inexperienced.  Or possibly you feel you have not acquired the necessary skills needed to give a good presentation. 

The Nervous

It may be nerves simply because this is an important event for you.  These are all good reasons.

These can be managed and even coached to lessen or dispel those feelings in order to give a good presentation.

After good training and good preparation, you can begin to have confidence based on an ‘appreciation of your abilities or qualities’.

Things like:

You have put the work in and you know your script.

You have done this successfully before.

You have had training and worked on your strengths to hone your skills.

The Overconfident

What is the thought pattern of those who are towards the very confident end of the reality spectrum?

Maybe they have experience in speaking, have received great feedback, and enjoy many compliments on their abilities. 

However as mentioned earlier, confidence is appealing, but arrogance is not.

How do you ensure you do not sound arrogant when you are confident?

First the antidote to arrogance is Humility.  A humble person recognizes their limitations, and view other people as important.

 The most important person in the room is the listener, not the speaker.  The speaker is there to benefit the audience.  Without the audience the speaker is just talking to himself.  Showing appreciation and respect for the audience is a good start to subduing an arrogant persona.

If you are speaking of your successes, do you need to claim all the glory?  Or, did your idea work because a talented team helped to accomplish your vision?  Spreading success to others shows a generous spirit which will appeal to your listener.  

Another good tip would be, rather than telling everyone how great you are, why not allow others to do it for you. 

No one is impressed by someone who likes to blow his own trumpet.  So, if you really have to tell others how great you are why not quote some client feedback, or recent email of thanks for what you have done or helped with.  

Somewhere between terrified and arrogant there is a comfortable resting place called reality.  The best way to ensure you have a realistic view of your abilities is to get feedback from a good friend.  I say good friend because only a good friend will tell you the truth instead of what you want to hear. 

A session with a good speaking coach can really help in this regard.  The advantage of an experienced coach is they are accustomed to not just pointing out weakness, but knowing where and how to improve. 

This will give you assurance based on an appreciation of your own abilities or qualities. –  Reality.