Love.
It is a powerful emotion, the feeling of sheer ecstasy when in the presence of one the heart yearns for. It's the feeling of intimate connection deeper and more exhilarating than any on Earth. The feeling as though the entire world has disappeared and the only thing that is left is the two lovers locked in each others' embrace.
Caramel Apple knows this all too well. He has been harboring secret feelings for a certain unicorn for a long time, almost since they first met. But he has a problem; she's a high class filly from Canterlot, who has studied at the finest school in the realm and has a personal connection the Their Majesties themselves. He's just a working-class schlub who was born and raised in the boondocks who makes his living getting his hooves burned in his blacksmith's shop. He knows that there isn't any way that Twilight Sparkle will see him as anything more than a good friend.
Just goes to show you how little he knows.