Why do I still worry about being left alone after all these years?

I can't shake this idea, maybe it was a dream, that I've worried over for 30+ years. One part has already come true, due to circumstances that couldn't be avoided. Now my children are starting to move away. I'm not afraid to be by myself, really it's a sad sad feeling. Incidentally, I have had other things come to me that quickly came true, but not that often. I told two of my kids last year that I'm going to be alone and they said I wouldn't be. But, like I say, one has since moved away, due to a new job.