I've been rejected by my top choice twice.
First time I applied to do Medicine. Like you, I went to a grammar school. Had stellar predicted grades, a killer personal statement that even had the personal seal of approval of one of the harshest teachers of the school. I got an interview at Oxford and then I blew it and I got rejected. It was very hard, and then I proceeded to not get a single offer for Medicine anyway. That wasn't fun at all. I can confidently say that was the second lowest moment of my life. But I just largely got on with my days. I let out my thoughts and feelings to the people I knew that were there for me, and thought to myself that it was the university's loss and that I'd go do great things no matter where I ended up. It was also at this time where I came up with the car analogy - universities are cars, they're a mode of transport to get you somewhere in life. In my case, I thought of Oxford as a Ferrari. Obviously, getting a Ferrari would have been amazing but I didn't, and in the end of the day, another university, another car (say, a Vauxhall?) will get me where I want to go in life too, which is all that matters in the end. That analogy helped me.
That first year though I only received an offer for Biomedicine at Newcastle, which I saw as an unacceptable vehicle - nothing more than a scooter that I can't even take out on the highway, so I went for round 2, this time applying for psychology. I applied to Oxford again in what can only be described as a terrible "Oh what the hell, why not?" moment, and I was rejected again. I did see that coming from a mile away though so it didn't hit me too hard the second time. This time around, I did get an offer I was happy with and so I went for it. In fact, I was so happy with this offer I eventually ended up withdrawing my application for KCL because I knew I'd rather go to Queen Mary than face going to KCL. Was rejecting KCL a power move? A moment of sheer madness? I like to think both.
I'm not going to lie to you and say that Queen Mary is as good as Oxford. But, you know what? It was possibly the best thing that could have happened to me. I don't want to bore you with my life, but I just fit here. I'm happy, I'm myself, I do great things that are massively setting me up to succeed in the future, I do silly things... and I just don't see all of this coming together as seamlessly and perfectly anywhere else. So, the second thing that also helps me deal with failure, is that I know life has a funny way of making things work out in the end.
Hope you're OK

SY