What is the most difficult sort of thing you have ever had to try to describe in writing?

  I do a lot of writing, and when describing people, places, things, events, actions, etc., I have always had a penchant for doing so in extreme and intricate detail, which requires a focus on such minutiae that I try to achieve an accurate word-picture for the readers. As such, answering your question is both very difficult for me to do in a simple manner, and simultaneously very easy use as an apt example of same. 
  I believe some of the most difficult scenes to describe are intimacy between two (or more) people, because each motion and reaction for each party creates an opportunity for yet another following or opposite action to be recounted.

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