Thorin worried for weeks over just how to confess his feelings to Bilbo. At first it was the thought that he shouldn't say anything at all; that falling in love with a hobbit was not what his company would expect of their dwarf king. When he finally shook that concern, he began to agonize over saying the wrong thing and making a fool of himself before he had even gotten started - and how silly that worry felt, because he had never been so desperate for approval before Bilbo. After days of carefully picking his words, the awful and sudden realization that Bilbo might not return his feelings occurred to him, and he nearly gave up on the whole thing, resolving to just try and ignore the attraction.
But in the end, he needn't have fretted so much, because when he finally managed to get the words unstuck from his throat, Bilbo simply looked at him with amusement in his eyes and said, "I know," as plain as though the whole world was already aware, and Thorin himself had been the last to realize it (which, as it happened, was exactly the case).
"You know," Thorin repeated, more of a statement than a question, surprised as he was to hear that answer from Bilbo, and not one of the many reactions of shock or desire or horribly awkward silences that he had conjured up in his head late at night. "How did you know?"
Bilbo raised an eyebrow at him as he continued shredding herbs into the pot he had set to boil over their campfire, seemingly not at all bothered by this unlikely turn of conversation. When he realized Thorin was asking an honest question, he dropped the last of the leaves into the pot and wiped his hands on his pants (a nasty habit he had picked up in the absence of pocket handkerchiefs). "It was in your eyes, the first time you looked at me, that night at Bag End," he answered. "You look at everyone else like you're expecting them to disappoint you. But when you look at me, it's like you're waiting for me to surprise you. And I'd say I just did," he added, grinning at the dumbfounded expression on Thorin's face.
He stepped close to the dwarf then, placing his small hand on Thorin's jaw and leaning close, head tilted up and something playful dancing in his eyes. When his lips were but a hair's breadth from Thorin's, eyes focused there with a burning intensity, he murmured, "It won't be the last time," and pulled back, looking entirely too pleased with himself as he turned and went back to preparing their supper, leaving the dwarf speechless and uncharacteristically flustered.
And from then on, Thorin worried for entirely different reasons altogether.