I know that everyone has their own theory as to why I've fought to keep Spike alive. Giles believes I can't see past my feelings for him, whatever those feelings are. Spike himself thought it was because I needed the pain he caused to keep myself going, to keep feeling, like it was before. Willow, Xander, Anya, Dawn, and even most of the girls all seem to think it's because I'm in love with him.
But what I feel for Spike is not love. At least, it's not the kind of love you see in fairytales, something good and pure and warm that fights through the darkest nights. What I feel for him, be it love or something else, was forged in the darkness. It feeds off the shadows inside us, the violence, and yet, it is gentle.
But that's not the real reason I've fought so hard for him. I loved Angel with all my heart, and yet when the world hung in the balance I was able to drive a sword through him and send him to hell. Love does not supersede the mission, my mission: to protect the world from the things that go bump in the night, no matter what the cost.
No, the real reason that I kept Spike my side was much simpler than love: death. Death is the Slayer's gift, and I give it out quite frequently to the evils that haunt this world. It is the reason I exist, to dole it out, to protect the innocent from it, and to pass my power through it when my time comes.
With Spike by my side, I could fulfill my mission. He was my partner, my companion, the one who had my back in every fight. I could fight twice as effectively because I knew that he would protect my weak spots, just as I was protecting his. I didn't have to look for him to know where he was. I could sense him, but it was more than that. I trusted him to be where I needed him when I needed him there. We were more powerful together than we ever were apart. And that is why I couldn't let him go.