Recently I've felt this more and more.
I'm married but dh isn't particularly bothered about me. I have parents but my mum told me at the weekend that having children is thankless and the happiest people she knows are single without a family. She said I should advise my own children not to have children but to get careers that paid well and just look after themselves as she has wasted her life.
I have no siblings (just me that's thankless then!) and no friends. That isn't strictly true I guess, I have what other people would probably call friends but if push came to shove I'm pretty sure I could disappear and it would make no difference and vice versa with most of them if I'm honest.
Pretty much when it comes down to the wire you're on your own aren't you?