What I learnt over the years as I improved at sailing was that you take decisions to consolidate your position and eliminate risk when you reach the place you believe you should be in the field. You don’t attack any more because you believe that if you do, you will probably lose what you have. In this situation, the allegory is in fact true.
If you want to win a race, you have to make race winning decisions and you won’t do that unless you believe you can win the race.
So why don’t you just do that, and then you’ll start winning?
Because you won’t and you shouldn’t. You should only make “race winning” decisions if you actually have the ability to win.
So how do you know when you should “believe”? That in itself is an ability you have to learn. In order to win you need to have the ability or skill, and you have to recognise a situation where your ability or skill means you can win. This is what the “believing” really is. Then you have to successfully execute and ride through the things you cannot control (the part that luck always plays).
I think that's mixing up cause and effect. People who succeed usually have reason to believe they will. Don't work on your belief; instead, work on your ability. You'll know you're ready when you think you can, realistically, succeed (though best to start as soon as you can do what you'll definitely be able to, and think you might be able to handle the rest, because learning as you go is often much more effective than trying to prepare for hypothetical eventualities ahead of time).
And it's a lie that you need to believe you will succeed. You just need to act like it. Be invested, and don't quit until you actually can't go on any more (unless there's an actual dead-end, like you've got a business with 70% of your target audience as customers and still can't afford to feed yourself with it). Though you might not need to compensate for this particular cognitive bias, if you're already practised at it.