quiddity
A quiddity is whatever makes something the type that it is: essence; a trifling point or quibble; a touch of eccentricity. If you fear you are in possession of odd quiddities as a writer - certain words, certain phrases, certain preferences for unlikely characters - embrace them, use them and follow them onto something new. A quiddity of mine, you ask? I use the archaic word methinks a lot, find excuses to use 'twas and wont, and put Latin into one or two of my characters' mouths although - nota bene (note carefully) - used sparingly.
What are your favorite quiddities as a writer?