I was thinking of Ten deciding to travel alone, because losing people became too painful, but we see Eleven forge new bonds (cautiously at first - see him threatening to send Amy home in 'The Beast Below' or the way he wants to run from River), but eventually hold onto his new friends, despite the pain, despite the fact that he knows he'll lose them, that they're never really be all his.

(Love the bit with Romana btw. Love, love, love. Because hope is such an important thing, and something Ten - to a certain degree - lost.)