In order to be able to do level design I think you need to be in a clear state of mind, focused only on the game and it's lore. Let the atmosphere of the game surround you until you are no longer distracted by outside factors.
What I learned about level design:
* keep it simple
* if there are too many objects on screen you get tired as a player
* clear up space on the map but make it so the player can use it
* you have to create and play at least 50 levels in order to really get well at it
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