Sometimes, when Arthur looks at him, he doesn't see him at all, he sees only a clumsy, annoying idiot of a servant who makes his day a lot more difficult than it already is. Whenever that happens, be it at a feast, on a hunting trip or when he's tidying up his prince's chambers, Merlin feels completely worthless in the matter of seconds. His vision blurs a little, his fingers start shaking and every fibre of his being is screaming, because Arthur's so near and still he can't even dare to reach out to him.
Sometimes, when Arthur smiles at him, it's icy and cold, arrogant and crushing. It always chills him down to the core, until it feels as if his blood and even his magic have frozen. His mouth goes dry and his chest tightens until it feels as if every breath is killing him, because obviously Merlin isn't good enough, isn't good enough for even being Arthur's servant.
Sometimes, when they spar, Arthur wants him dead, Merlin's certain of it. And it takes all he's got not to drop his sword or shield or whatever he's holding and let his prince end it. Because, if that is what Arthur wishes for, who is he to argue?
Sometimes, when Arthur says something about him being useless, Merlin knows he means it. It is then that everything starts to hurt, since if there's one single thing in the world, which Merlin wants, it's for Arthur to acknowledge him. To see him for who he really is.
Sometimes, when they touch (which rarely ever happens so that Merlin remembers every time), Arthur's disgusted. He notices it, because suddenly the contact isn't something to relish anymore, but instead it burns and rips and tears him apart, until there's nothing left. Or at least, that is what Merlin would wish for in those moments. For, if his prince doesn't want him, is there anything left that matters?
But then again, sometimes Arthur looks at him, and Merlin knows, just knows, that he sees past the façade he has put up, past their difficulties, them being master and servant, even past the magic, and just sees him. What he is, and what he wants to be and why. And then, his prince smiles, always does, and Merlin feels like he's invincible, since, if Arthur can accept him for what he is, nothing else matters.
And sometimes, Arthur smiles at him, not joking, or sarcastic or challenging, but warmly and full of emotions. Most of the times, Merlin smiles back without even noticing it, because he's been rushed through by pure joy and love. It's in those moments only that he can't deny it anymore: He's fallen for his prince a long, long time ago. And while his mind is still too clouded by warmth, he wouldn't change a thing.
Sometimes, when they spar and Merlin does an especially stupid thing like hitting himself over the head with his shield and Arthur is laughing, there's a spark in his eyes, so happy and carefree. It's enough to make him forget all of the pain and start laughing as well, for he can't think of any sound that rivals his prince's laugh.
Sometimes, although very seldom, Arthur says something nice. It always takes some time until Merlin's brain has processed it, and mostly his answer is not equally nice (because his brain is still working, but he has to reply so doesn't look that much of a girl to his prince, becoming all flattered and flustered because of a few kind lines), but the rest of the day, or the wee) the words are playing inside his head, filling him completely.
Sometimes, sometimes, they touch, and the contact lasts just a second too long to be considered strictly platonic, or Arthur turns his head and smiles secretively. It's then; that Merlin can't believe he actually doubted his destiny once, for this really, really is everything he wants; staying at his prince's side.
And finally they kiss. And Merlin can feel everything (the hurt, the tearing, the joy, the warmth, the uselessness, the love) simultaneously and pours it all in the kiss, hoping that his prince understands. And Arthur weaves their fingers together and one hand into his hair to get him closer and Merlin understands that his beloved has known all along.