"Because it is difficult, you need to perform it perfectly in order to have a successful potion. You know how I was during the torture, always trying to keep myself standing as long as possible. I needed to focus on something. First I thought of something Draco and I did in that room, but eventually I couldn’t remember it clearly anymore until the memories were gone. Focus was the best thing for survival, that was the last night the Dark Lord tortured me, so I remember," I explain. 