Self-confidence/assurance is simply all about being on a firm ground i.e. self-confidence/assurance is all about being 100% assured/confident of your self/potential/skill/ability/belief. Now that infers, whoever that is not assured/confident of his/her potential/skill/ability/belief is never self-confident/assured. So, dare to be self-assured/confident if you've not been self-confident/assured.