The biggest problem with these 'virtues' and 'vices' is that not all of them are conveniently opposites of each other. You know, like 'love' and 'hate'. You can recognize when you feel love and when you feel hate. And, if you are in the mood to be particularly virtuous, you know what you ought to do and what you ought not to do. Is it too much to ask that all things conveniently align themselves the same way? Apparently, it is.
Take this 'self-belief' and 'over-confidence', for example. I mean, to me both feel the same. Comes to a task that I have to do, and I feel that I CAN do it, why is it some times considered 'self-belief' and, at other times, 'over-confidence'? It seems to me like if I succeed in it, they laud my 'self-belief' and if I fail they blame me for 'over-confidence'.
My friends do not agree that it is all a matter of 20:20 hindsight on the part of the people who judge me. As expected. By now you know that all my friends are the sort who swear by the idea that 'a true friend is one who tells you bitter truths about yourself'. Only, they go one step further and think that, being true friends, they are allowed to say ONLY bitter things - true or otherwise.
So, apparently, the belief that I CAN do a task when I have not truly assessed whether I have the ability to do it, or do it within the time frame prescribed, is NOT self-belief but over-confidence. To know what the job requires in terms of capabilities and to assess whether I have them or not is, apparently, a prerequisite for it to be 'self-belief'.
It's like if I have never learned to sing and agree to perform on stage, it's over-confidence. If I have learned to sing but have never sung on stage, to fear to get on stage is lack of self-belief. To have learned to sing and to approach singing on stage with the confidence that you will be good, that's self-belief. That sort of thing.
Then what about the guys who become entrepreneurs, say, just because they know how to develop apps, with no clue about finance or marketing or whatever? They do not HAVE the abilities needed and yet...
Well, they had an answer for that as well. When it is long term, the confidence that you can either LEARN whatever is needed OR can hire those who know is all that is needed for it to be self-belief, or so they said.
In short 'self-belief' is the attitude that you CAN learn to be good at whatever you need to succeed. Over-confidence is where you assume that you are already good at everything you need to know!