There were many moments that Anakin Skywalker held close to his chest, a zealously guarded trove of treasures, that involved his master. From the first time Obi-Wan had not hidden the fact he'd been crying in grief for Qui-Gon to the light touch of Obi-Wan's hand on his face, wishing him well from the surgery for his arm.
Close to the top of the list, if not at the pinnacle, was one single moment, the blaze of Obi-Wan's pride in him as they parted ways. Even with all the turmoil that had lashed through Anakin since coming back to Coruscant, that pride could take away all the pain, all the misery.
He savored the light falling on his master's hair, cherished that small smile, reveled in the kindness of the eyes boring into him with both knowledge and faith. In that moment, full of potential, Anakin Skywalker even felt worthy of the pride.
Such moments, however, were never meant to last. The ephemeral peace took its toll by making the Fall all the more despairing, as Darkness closed in and blotted out the joy with desperation and horror.
When Vader faced Kenobi on Mustafar, that tiny moment was lost forever.