When someone breaks up with you, you have two options.
1. You can enter an extended period of mourning. You can blame yourself and say you weren't pretty enough or smart enough or fun enough. You can wallow, shun other potential dates, and remain convinced that you'll never find love again.
2. Or you can mourn–briefly–and move on, assured that there are plenty of good matches out there for you who will appreciate you for you who are.
The second option is far, far better than the first.
A college rejection should be treated like a break-up except for one crucial difference; break-ups are personal, college decisions are not. They might feel that way, but the fact that you were rejected does not necessarily mean that the admissions office didn't love your essay or appreciate your activities or think you wouldn't be a great addition to the campus. Sometimes is just means that there weren't enough spaces to go around.
Post-rejection dejection is normal. But wallowing in a college rejection, telling yourself that you might have gotten in if your test scores were higher or if you took another AP class or if your essay were just a little stronger, that's like beating yourself up after a break-up. It will only make you feel worse and delay your opportunity to find a better match.
The best thing you can do is accept the rejection and move on to one of the colleges who was smart enough and lucky enough to offer you a spot.