Wikipedia's <A href="http://en.wikipedia.org/w/index.php?title=Confidence&oldid=363515253">current description of confidence</a> and <A href="http://en.wikipedia.org/wiki/Self-confidence">self confidence</a> is nice:

<ul>
<li>Confidence can be a self-fulfilling prophecy &mdash; You can fail because of lack of confidence, because you presume ahead of time that you're going to fail, and thus never try.
<li>Reasonable confidence means being aware of the possible bad things that could happen, but not being preoccupied with them.  It means having the self-assurance that you can deal with any negative outcomes that may happen.  This attitude makes it more likely that you have positive outcomes, because you make those positive outcomes happen.
    <!-- <ul>
    <li>If you're preoccupied with negative outcomes, then you're probably being too pessimistic.
    </ul> -->
<li><a href="http://en.wikipedia.org/wiki/Self-confidence">"Promise yourself, no matter how difficult the problem life throws at you, that you will try as hard as you can to help yourself. You acknowledge that sometimes your efforts to help yourself may not result in success, as often being properly rewarded is not in your control."</a>
</ul>