Tony looked forward to entering Abby's lab- she was the only one who could truly brighten his day. Her shiny black hair, her dark eyes, and her gorgeous smile- everything about her made Tony happy. Except that she wasn't with him. That is what he wanted more than anything. To wake up next to Abby, to share his secrets and ideas with her, and for her to be as close to him as he felt to her. He relived how happy she seemed when he was back from Y-Pestis, and how the only thing that took his physical pain off his mind was the warmth he felt from her as he lay next to her, thinking how innocent it was and how much more he wanted it to be.
Although the more her thought about her, the more he knew that this was more than physical attraction. He wanted to know her, more than he had wanted to know anyone ever before, more than he knew Gibbs and Kate, Ducky, and he enjoyed being around her more than he enjoyed torturing McGee and Palmer put together.
What made Tony feel worst of all is the fact he knew Abby didn't feel the same. He felt the shame of falling desperately in love with one of his best friends. Best friends that were so similar but too different to be anything more, Sometimes Tony imagined life with her as his, but he tried to refrain from straying there. Hiding his emotional pain was easy- bragging about other women made him seem unavailable and he didn't want to be that guy anymore. He knew nothing would ever make him as happy as Abby did, nor could anything make him sadder.