My dear you are very much correct. It's good to have confidence in us as regards to what we can do, where it becomes dangerous is when it turns out to be overconfidence, reason being that there's limit to what everyone can do. I am not against people believing in themselves but we must know that things may not always be the way they appear (in your words).

Again I like the example you gave regarding the task that proved tough but you conquered it,this is because,you have some knowledge regarding it. Whereby you just said I can do it knowing fully well that you are not knowledgeable in it would have resulted to to you being over confident. Best Wishes with the contest 💯