The thing about Nightmare is items become pretty key later in the game. Earlier on, you can get away with hiding mostly. Later on, it's multiple aliens, and some situations are just plain cheap in spots can actually force you to use items, which is fine. But if you use too much ammo or materials early on, it can hurt you, in the end of the game. And while there are caches throughout the game, materials and ammo are pretty friggin scarce on Nightmare. It just feels like one of the funner aspects of the game is less prominent on Nightmare precisely because you never want to use up any of your precious flares or crafting components if you don't have. Sometimes, it's just better to die, and redo a section over than to use a pipe bomb or a noisy box to save your life.