If you haven’t read Harry Potter and the Chamber of Secrets, you might want to skip this post.
People come up with a lot of analogies for describing what it’s like having intrusive thoughts. My current favourite way of expressing how hard it is to talk about the specifics of them is that it’s sort of like being Dobby while he’s still enslaved to the Malfoys. You’re trying to communicate that Voldemort* and Lucius Malfoy (i.e. the self-destructive part of your brain) have a cunning and dangerous plan afoot, but when Dobby gets as far as Harry Potter’s house to warn him (i.e. you get as far as the doctor’s office to try and tell them what’s in your head), you get distracted by how angry your evil master (Malfoy/brain) is going to be with you for spilling the beans. Then you spend half an hour telling the psychiatrist, “Dobby will have to punish himself most grievously for coming to see you, sir. Dobby will have to shut his ears in the oven door for this,” or sitting in silence punctuated by occasional exclamations of “Bad Dobby! Bad Dobby!”
Fellow fans will remember that Dobby is freed when Harry tricks Lucius Malfoy into accidentally giving him a gross sock that got covered in slime somewhere along his (Harry’s) journey into and out of the Chamber of Secrets. A very literal-minded friend did offer to find me a mouldering sock from her teenage son’s room, so it’s possible you can over-stretch an analogy. But it does kind of work, because people who’ve “recovered” (whatever that means, and it’s a lot more open to debate than you might think) tell me that it’s less about not having the thoughts than about breaking the link between thinking and acting. Just like the newly sock-equipped Dobby can still hear Malfoy shouting, but he doesn’t have to do what he says any more. See? Perfect.
* Incidentally, I’m often tempted to respond to professionals’ over-reliance on euphemisms with, “Always use the proper name for things. Fear of a name only increases the fear of the thing itself,” but I feel like the kind of psychiatrist/nurse who constantly talks crap probably isn’t a Dumbledore fan anyway.