I'll be having a good day. 

Then BAM.

My mind takes me to terrible places. That I am going to get in a car accident that'll be fatal to my toddler, and then I'd have to kill myself.  Or that i get diagnosed with something terminal and I'm having to prepare my daughter for when I'm gone. Or that my dog gets hit by a car. Or that I accidentally killed someone and I'm on trial and sent to prison. Or that my husband gets hurt or killed by accident.

And then I'm crippled with anxiety for no reason, while my mind plays through the possible aftermath of each scenario. 

Why does my brain do this multiple times a day? Especially when I'm falling asleep?
How do I get it to STOP?