Now that there are no other Time Lords left (for all intensive purposes) to impose upon the Doctor their roles of time travel, he grows a tad mad with power in developing the notion that "time can be rewritten" (first said in "The Forest of the Dead"). In the episode "The Waters of Mars," his actions cause a charcter to take her own life. In the next episode, "The End of Time", his conscience is heavy from that. He says: "It's not like I'm an innocent. I've taken lives. And I got worse, I got clever. Manipulated people into taking their own." At this point, he sees himself in a very negative light, almost wishing for his own death (and he does "die" soon), thinking that "Time Lords live too long" (End of Time pt. 2).Throughout the span of the Tenth Doctor, he becomes an increasingly selfless person, almost verging on the point of being so willing to die that it seems that he wants to die. It culminates when he frees Wilfred Mott (Donna's grandfather) by taking the dose of radiation that causes him to regenerate. From what we have seen so far from the Eleventh Doctor, that seems to have gotten his death wish out of his system.
Although the combination of fishfingers and custard may have been a huge risk.
