I've thought of it too! I'm actually quite paranoid. Almost everyday I think about death in one way or another. I'm morbid.
However, I'm one of the most cheerful person anyone could meet. I could win a smiling contest for smiling the longest, but I am very dark inside. Oops, that was supposed to be a secret. I guess you all know now.
I know I'd freak out if my partner died. There's no benefit in dwelling about that now though. When it happens, it happens, and I'll think about it when it comes.