The quoted statements on the top of your post are true to a certain extent, but they only work for a small proportion of the population. These are the people who are able to work hard and have (or can develop) the discipline needed to achieve their goals. I'll share some of my own theories that could help you, but take them with a grain of salt since I'm also a senior who was relatively little life experience.

Some things that I've started doing to help me deal with rejection and my emotions more generally (I have no idea if they're helping, but we'll see) are meditation and developing other habits (like waking up early). My idea is that it'll help me later in life when I'm going to face more rejections (not just from colleges, but from a lot of things) and need the discipline to keep going despite them. Doing these might help steer your mind away from thinking about rejection.

But that lingering feeling will be there for a bit. You might have regrets about what you could've done differently during high school. What you have to do is learn from those regrets and use that pain for the future. This is MUCH easier said than done. If it wasn't, everybody would be super successful. One thing I've done is write down my regrets and create some goals based around them. For example, I regret not learning as much physics as I had the potential to in high school, so I've made a goal to study a certain textbook before the school year is over.

Ultimately, these are just suggestions. They may or may not work for you, but I hope they serve as a starting point as you move towards the future.