I need to go to A State of Some Confusion, but I have a Memory of Light, so whenever my Nightmares gets too high, I go to the Mirror-Marshes instead. Is there any way I can go to A State of Some Confusion without selling my Memory of Light?
You can't disable your Memory of Light, but once you're in the Mirror-Marches, there's an always-available storylet called A familiar scene? that will take you to A State Of Some Confusion.
Or, as you've realized, you can just sell your Memories of Light in the Bazaar these days. If you need it back, you can just buy some Lamplighter Beeswax and convert it upwards through Phosphorescent Beetles and then to Memories of Light again.