Worst dreams/thinking worst thoughts - why?

OK, not quite the same as ‘the dream you had’ or dream interpretation, I’m just wondering if anyone does this and also if anyone has an explanation why I (or others) do it.
I will often dream the worst dreams imaginable. My wife dies or I lose one of my kids, either they go missing in a busy street or [specifically] drown. Now, these aren’t always dreams - sometimes they are simply woken thoughts. I may be sitting watching TV or reading a book and I end up torturing myself thinking what would I do if child #1 suddenly fell into the road and was killed by a car. I couldn’t kill myself and leave the others so I’d literally have to live with the grief for the rest of my life. Yeah, I know - weird…
I don’t subscribe to the opinion dreams mean something (further than something playing on your mind) or are some mystical way of forseeing future events. I understand that these things I think/dream about are my worst nightmares (literally) but what I can’t figure out is WHY my brain decides to do this to me? It affects me. A lot. It makes me pretty damn upset and freaks me out.
I’m sure there is a ratinal explanation - anyone care to suggest what it might be?

IANAP (I am not a psychologist/psychiatrist - but I did study as one ages ago), but my wild-ass guess is that you have some anxiety that comes out as these awful, helpless feelings and weird thoughts, and that anxiety comes out in your dreams too because you’re feeling it so much during the day. Part of it might be related to work, to being a father and the responsibility that goes with that, and so on.

My recommendation is to check Amazon and search for a Cognitive Behavioral Therapy book - or better yet, workbook - that has good ratings from readers and seems to relate to how you’re feeling. I know there’s an author named Knaus that has written some good CBT books.

CBT focuses on pointing out irrational thoughts and feelings, and helps you find ways to confront them with logic so you can calm yourself and dismiss those counterproductive thoughts. Hopefully you’ll find something helpful.

In the meantime, try to find some simple thought that calms you when you’re having one of those intrusive thoughts in your head. Something simple like, “That’s not reality,” perhaps. And don’t get anxious when one of these thoughts pop up, as it just creates a “feedback loop” of making you even more anxious. Accept that it has happened and find a way to shoo it out quietly.

Thanks for your reply.
Yeah, that’s how I dismiss it. Saying to myself “not real, not thinking about it”. That tends to work well during waking hours, but not much use when I’m knocking out the Z’s. Most times though the dream is bad enough to wake me, which leaves me awake in the dark wondering why the hell I just dreamed that…

I’m off to read up on your suggestions there. Much appreciated.