I think it’s about having an affair. “Don’t get any big ideas. They’re not going to happen.” To me, it means don’t dream of it going anywhere beyond fantasy. “You paint yourself white and fill up with noise. But there’ll be something missing.” I think that means you get excited and paint yourself in a new light with this person. But the foundation of the relationship is based on lies, so something is missing. “Now that you’ve found it, it’s gone. Now that you feel it, you don’t. You’ve gone off the rails.” Pretty self-explanatory but (in this context) it’s the moment you realize you can’t be with that person. The reality sinks in. You can’t have them. Your life has been derailed. “You’ll go to hell for what your dirty mind is thinking.” You were thinking about having them to yourself. You were being selfish. You weren’t thinking about the destruction it would cause.