You don't have to be attentive to be confident. In fact some of the most confident people aren't really sure why what they do works, they just know that it does.
Competence on the other hand is a measure of how much you know about a subject or how many distinction you make on an activity. To be competent you really have to know what's going on. It requires you be attentive and constantly learning.
I think this probably makes sense to everyone. Where this is significant is if your competence is growing and growing, i.e you are learning more and more and getting better and better at something, your confidence should be growing at an equal rate. Having your confidence grow will encourage you to try new things, which will inspire new learning. A competent person who is lacking in confidence will have a lot of distinction about a subject, but lack a fervor and passion to explore.
Someone who is confident may not necessarily value competence, or understand it. We have all had moments when we were sure that we truly knew something, or were going to succeed. If confidence grows without having competence grow, we find that we don't really know why we're great. We also don't know if we're great because that would require getting information from others, which we may not think is necessary, since we know it all.
Confidence can be addictive because it can tell us that we don't need anything else and that we've grown enough. Competence has a similar pitfall. We can think if we just learn one more thing, then we'll feel confident, which may never pan out.
Rather presence bridges the gaps between confidence and competence as they both grow, which deepens our understanding of our chosen interest AS WELL AS ourselves.
---> a little bit of info I picked up from the Mind Relief Manuscript. Well worth reading and free, you can pick it up at Jerry Stocking's (the king of self development) homepage