Afterwards he blames himself for not seeing what was coming, for being so blind to what was going on underneath his nose that he was caught completely unawares. It's not like him to be so oblivious to the undercurrents - that's Grissom's schtick, not his.
Strange then that Grissom's the one who saw it, although in the end both of them were powerless; him to resist when Sara finally responded to his flirting and Grissom to respond to hers at all.
But when the explosion comes, it shatters his life, not theirs. They played with fire, and he's the one burnt.