"Don't go thinking this is goodbye, Wilf. I'll see you again, one more time. Just keep looking. I'll be there." Wilf asks where he's going; a smile plays around the edges of his sadness.
"To get my reward."
The etymology for the name "Orpheus" is really hard to pin down. "To be deprived"; "to put asunder, to separate." "Darkness," orphanos, "to lament, sing wildly, cast a spell." Orpheus was defined by loss and the failure of faith. You look back -- at the end of life -- and if you're not willing to give it up at that moment, you never deserved it in the first place.
Martha runs through an abandoned lot, awesome braids swirling around her head, fighting a Sontaran. Mickey covers her as she breaks down an alley, yelling at her to stay behind. "You looked like you needed help. Besides, you're the one who persuaded me to go freelance!" Mickey laughs. "Yeah, but we're being fired at by a Sontaran. A dumpling with a gun!" He takes her into his arms. "And this is no place for a married woman." They laugh, and kiss, and as a disgusting Sontaran licks his lips and takes aim at them, the Doctor downs him with a cartoon mallet. Martha looks up as Mickey plans their next move, and spots him. He doesn't smile, or wave. Just looks at them, lovingly, long enough they'll know this is it. She takes Mickey in her arms, and they weep.
Luke runs across the street, talking on his phone -- Sarah Jane's got some story going about how wi-fi went mad all over the world and everybody was hallucinating -- and narrowly misses being hit by a car. The Doctor whips him out of the way, and Luke runs shouting to his mother. She looks across the way, and sees her Doctor, shining in the sun. They wave, and she smiles, and weeps for him. Not sad, not happy for anything but to have seen him at the end. Her smile says hello, and goodbye, and the same time. Her biggest smile.
It's the humanity in the Doctor, which Martha and all the Companions have forged and will continue to forge, that keep him on the path. Life is balance and it's a constant working: Grace is a wave that never breaks.