This is based on spoilers for the 100th episode and remainder of season 5. Booth POV.
I don't. I can't. I won't.
Those are the words that Booth couldn't drink away, couldn't sleep away, couldn't smile and laugh and pretend away. He hears them still, in her choking pained contralto, her arrogant eloquence shattered on a DC sidewalk after he'd stepped over his own line and broken them both. He wonders how long he'll be replaying that scene in his dreams: her wide stricken eyes, the taste of tears as she kissed him, how she clung to him and told him she loved him and she believed him and it still wasn't enough, she was broken and she was breaking him too and there was nothing either one of them could do about it.
I don't know how to be with you like this.
I can't be what you need right now.
I won't risk losing you.
And he knows better, knows her better and knows them better and knows that for once in her life, Temperance Brennan is absolutely and utterly wrong; and he knows also that all the evidence she has gathered so far in her life has convinced her that she is right, and until sufficient evidence to the contrary can be presented to her, she will not be swayed. She wept in his arms and clung to him and declared her love and kissed him with a drowning desperation, but still it was don't and can't and won't that he took home with him that night, and he remembered something she'd said to him once, another time when her voice was breaking and her eyes were overflowing and he'd wondered how he could've ever thought her cold:
It really was heartcrushing, to think that no one loved you. But to know that someone did and it still didn't change things? That was worse, so much worse, to bear.