I would probably be Honesty.
For all my bad traits, I am honest, if nothing else. Not to mention I'm as bad a liar as Applejack.
Were I to choose an Element to best describe me... perhaps Element of Hope. Despite often being rather negative, I do hold a very strong sense of hope in my heart. (I know because if I hadn't, I would have given up long ago with all the stuff I went through last year and the year before.)
Sadly, despite my hopes, I have not yet been asked to join the Blue Lantern Corps. Drat.