Why do some people fixate on a method despite knowing it's a bad idea?

[Otter]

Me thinks down deep, they don't really want to die (they know it will fail). They're just not quite ready. Maybe?
My second thought is that they want to go out as the one who finally conquered a certain "impossible" method.

 

[BridgeJumper]

Yes, this ^
I started with ODs on the most unreliable substances, or cutting my wrists, because I wasnt ready. I knew I wont die but I will get help once I do it.
I fixate on jumping really bad. Constantly searching for the tallest bridges I can find and easily get to. Im attracted to how fast and reliable it is.
I have also fixated on train and overdoses, even though I knew the first one would hurt the driver and I didnt want that, and the second one will not work. I dont know why. Weird and unknown specifics of my brain I guess