John Henry

House Season 1, Episode 9. The character John Henry, the best trumpet player around, suffers from symptoms that seem to 'take away [his] air'. Without the use of his lungs, he can't be a trumpet guy. To him, if he can't be a trumpet guy, he isn't anything. He signs a Do Not Resuscitate form - he wants to die. House does resuscitate him, and has to go to court to prevent the plug from being pulled on John Henry. When Dr. House talks to him, he stares House straight in the eye and says:

... I know the empty ring finger.  And that obsessive nature of yours, that’s a big secret.  You don’t risk jail and your career just to save somebody who doesn’t want to be saved unless you got something, anything, one thing.  The reason normal people got wives and kids and hobbies, whatever.  That’s because they don’t got that one thing that hits them that hard and that true.  I got music, you got this.  The thing you think about all the time, the thing that keeps you south of normal.  Yeah, makes us great, makes us the best.  All we miss out on is everything else.  No woman waiting at home after work with the drink and the kiss, that ain’t gonna happen for us.

I could have been standing there in House's shoes. Instead of medicine, it would be fencing. When I say I feel like I don't have an identity, it's because I'm subconsciously looking for 'that one thing' again.