Regret

The theory of what happens when a human becomes  vampire in The Vampire Diaries, is that as a vampire all the emotions are heightened to catastrophic levels. So when u're happy.. you're ecstatic! And when u're sad..  you're suicidal!

Basically, they lose all sense of balance and become a study in extremes.. two opposing polarities forced to inhabit a singular physical form.

Hence, the concept of the humanity switch. Those vampires which have too much compassion as humans, end up getting the short end of the stick since.. well now you need to suck the life force out of someone... and it feels REALLY REALLY CATASTROPHICALLY BAD!!

So these poor oversensitive souls, with seriously low threshholds for emotional pain.... they have the option of flipping their emotional switch to off. Not feel anything anymore. Comfortably numb!

Then its all good.

I think i'm a vampire.