On his worst days, Mark feels like he doesn't exist.

He counts up the people in his life and has to face the fact that each and every one of them has a life that he's not in. Their real lives, their bottom lines, the lives, the people they'd die for.

That he would die for any of them is something he keeps to himself. He's trying to master boundaries and that's one you don't cross with people who don't quite feel the same way. Sure, there'd be good intentions and kind words and that means something, means a lot, and he's not taking it for granted; but there's an imbalance, one that would embarrass the people he loves and hurt him more than he wants to be fully exposed to.

So he keeps it to himself and smiles, jokes, helps out when necessary, offers advice that comes out wiser than he ever knew he was, and that he doesn't stand a cat's chance in hell of ever following himself, but seems to soothe others.

He keeps it to himself and he works. It's as close as he gets to a bottom line, the one essential reason for his being on the earth. He's good at it, genuinely so good that even his self-doubt knows it for a fact. He's good at it and he's strong, calm, seen it all before, even the worst burns, the most destructive scars. The patients need him and he comes through, a replacement opportunity for what never quite works out when he's off duty.

On his worst days, he feels like he doesn't exist. Until he tells a family their kid's okay, or reassures a frightened husband and for a moment, until he fades back out of their world, it's almost like he's real.