Someone or something you definitely could live without.
My husband. I know it sounds cliche, but it's very true. I know in my head that if I HAD to go on without him, I could. But I know in my heart that if he were to die or leave, part of me would go with him.
A few years back he had to go away for 6 weeks, and even through my working like a mad woman, dealing with an infant and being hugely pregnant, those were the longest, slowest days of my life. It was like I could hear the seconds ticking, and everyone of them broke my heart. It really gave me a new understanding of how hard it is for military families! I think I would go insane if it were a "normal" thing for us. Hell, there are days when the idea of him going to work makes me want to cry!