After Klaus killed Elena, John sacrificed himself to bring her back to life, by which he needed a witch to bind his soul for her, so Bonnie offered to do the spell, for him to save his beloved daughter.

Around that time, Elena learned he was her biological father.

After finishing his job, Katherine attempted to kill him, but failed and John left.

A few months later, he returned with Isobel to help protect Elena from Klaus.

Dan Gilbert, author of "Stumbling on Happiness," challenges the idea that we’ll be miserable if we don’t get what we want.

Our "psychological immune system" lets us feel truly happy even when things don’t go as planned.

Harvard psychologist Dan Gilbert says our beliefs about what will make us happy are often wrong — a premise he supports with intriguing research, and explains in his accessible and unexpectedly funny book, Stumbling on Happiness.Johnathan "John" Gilbert II was a major recurring character and an antagonist of the first and second season of The Vampire Diaries.He was Grayson Gilbert's younger brother and is Elena Gilbert's biological father.He met and fell in love with Isobel Flemming when she visited Mystic Falls before she turned into a vampire.After she turned, John left town for a while before coming back in Under Control. John, along with Alaric Saltzman, possesses a ring that prevents its bearer from being killed by something supernatural. John gave his ring to his first former lover Isobel who then gave it to Alaric, her husband.After Grayson Gilbert died, John inherited his ring.