Disclaimer: copyright holders include Joss Whedon and Mutant Enemy Inc.
"Effulgent love, laughing death."-Richard Wagner, Siegfried
Spike glimpsed Buffy alive, dancing and happy. Then he left. He could not bring himself to cash in on his sacrifice or her feelings. It had not been his choice to take back his gift to the world by returning. He did not take back his gift to her.
He did not lose her gift to him. She had let him be with her as he most needed. He wanted burning, consuming love and he needed her to go on living.
He saw their hands together catching fire. For the second time he managed to save her from the fire in which she was starting to burn. He warded off her declaration of love with a quibble--her trusting love was not his fatal passion. After he dismissed her back into her life, he laughed with delight at the destruction which he had created and the love he had saved. They had stood together in light which he gave her and which would shine through his lives and his deaths.