Game theory explains why advice from successful people is almost always useless. You are studying survivors, the ones who endured hardships, collapse, and catastrophe. And survivors frequently cannot see the graveyard. A thousand people ran the same aggressive strategy, and one of them, the person you're speaking to, happened to be the one to make it out. The useful advice is never what the winner did. It is what the winner did that the losers did not, and that's the question they frequently don't answer. Study the graveyard, because everyone still standing has an enormous incentive to believe it was skill.
Most people who lack self-confidence actually lack initiative, and they lack initiative because they lack self-respect for the time they were conferred on this planet.