"You only live once," is a human justification for so many things. It make even make sense for them. But what would the Gallifreyan version of it be—"you only live thirteen times?" Not nearly as short or interesting.

Now, they also say you never get a second chance. But he doesn't believe that either. He's given second chances to so many enemies. Sontarans. Slitheen. Cybermen. Daleks. He's lost track of how many times he's faced the 'last' Daleks. Every time he thinks this is their last chance, they prove him wrong. Maybe he should stop thinking it, even if he still says it.

But that isn't the biggest problem with the saying. The worst part is when it is true. It is true with his friends. He didn't have a second chance to take Sarah to Gallifrey, to save Adric or say goodbye to Susan. No second chances for his friends.

Only his enemies.