In way, it has to be one of the toughest speeches he's ever given. No one wants to show up and face the music after you've lost, although he can take some solace in the fact that he personally never lost. But his side did, and to the extent Hillary based her campaign on the idea that she wanted to continue his legacy, he lost big-time.
And yet, when you're on the losing side, in many ways the pressure's off. All you have to do is show a basic modicum of grace and people give you credit for showing class. It's really not that high a bar to clear. But give credit to Obama. When he wants to be gracious, he's very good at it, and he knew that today he had no other option: