Until he regained his soul Spike never knew there was a difference between love and desire. When he was alive, love was a romantic ideal, for which he would always strive but probably wouldn't attain. Love was poetry and sweet words, and desire, that was something to be ignored until the wedding night, or, if unable to be ignored, to be sated quickly and unsatisfactorily. Mental self-flagellation followed those moments of weakness, driving away any lingering lust, allowing him to return to thoughts of pure love.
Once turned, desire was sated between the pale, cool legs of his goddess and for one hundred and twenty years, love and desire were one. Hot passion and biting love and a wild ride of pleasure. He loved Drusilla with all his dead heart. He lusted after her with an enduring passion. Both were dark and erotic states and he thought those were the truths about love and desire.
When he fell in love with Buffy, it was dark and unwanted. She refused to accept it, he hated feeling it. It was easier, more normal, to lust after her and satisfy that lust when she finally let him. The pleasure was real and the desire was real, but the love hurt them both, culminating in a night on her bathroom floor he couldn't regret until his soul returned.
After the restoration of his soul, he saw the truth. Regrets brought him back to her, but once he got past that, once he regained his sanity, love kept him at her side.
Real love. Not an ideal. Not poetry. Not hearts and flowers.
His love was still a bit dark, still a bit dangerous. His desire for her never faded.
But, with a soul, he knew the difference. With a soul, he let love reign over him, not desire.
There would be no repeat of that night in her bathroom.
There could never be.
He loved he with all his dead heart and all his living soul, and he knew his desire could wait, forever if necessary, for her to love him back.
Desire without love wasn't something he wanted. Not anymore.
Not with Buffy.
End