From Everyone Brave Is Forgiven by Chris Cleave:

He moved his face close to hers. “When I said ‘I love you’ before?”

“Yes?”

“I didn’t mean it. But now I think I do.”

“Oh yes. Oh, me too.”

Tom understood why the good actors in the movies never said it with a smile. To be in love was to understand how alone one had been before. It was to know that if one were ever alone again, there would be no exemption from the agony of it. It wasn’t the happiest feeling.