This is what many educators call a 'teachable moment'. Time for an actual philosophy lesson!

What we have here is an illustration of mixing up the necessary and sufficient conditions for something to happen.

Believing that you can do something might (at best) be a necessary precondition of success - it's hard to be really successful without at least a little self-belief.

But it isn't sufficient for success - it takes much more than self-belief to achieve anything.

For example, I believe that I'm a passable philosopher and that I can write a pretty good article. This belief is a necessary precondition to my articles ending up on the trending page (because if I didn't think this, I wouldn't write or publish). However, this belief is not sufficient by itself to get my articles to the top of trending - it's not even enough to get them to the top of #philosophy.

A further illustration: It's a necessary condition of getting to the top #philosophy that I publish a post using that tag. The sufficient condition of topping this tag is that (at the time of writing this reply) I get over $430.64 worth of upvotes. Given that I haven't been here very long, and I don't attract many big-SP votes, this would mean spending more on bidbots than both you and @pinacle.

So, as you can see, there is more to being successful, or even surviving, than solely self-belief. It's important, but it isn't everything. This is really important for people to understand.

When you succeed, it's not just because you believed in yourself - it's due to your talent and hard work. It is also due to factors like your genetic predisposition, the geographic and socioeconomic situation you were born into, and random dumb luck.

Likewise, when you fail, it necessarily just because you didn't believe in yourself enough. Maybe you didn't make the right choices or work hard enough. Or maybe you don't have the right genes, were't born in the right country, don't have parents who were rich enough, and so on.

Sometimes your success or failure is down to you and your self-belief. Sometimes it's just the way the universe is, and no amount of motivational bullshit will change that.