Obi Wan cared for Anakin. He felt his doubts and turmoil's. He suffered with him his insecurities. Later on he'll consider himself partly to blame because of it. Because his compassion made him not to report such things to their elders. It made him to justify his emotions as natural, as longing for home, as an expression of his temperament.
There was a problem between them from the start. The problem of their age. Obi Wan wasn't old enough to be a proper master and Anakin never grew to respect him as he would Qui Gon who took him in. Surely Qui Gon would find a way to reach the boy. In his wisdom he surely did see the way for him to embrace the light.
But Obi Wan wasn't wise. He grew old still not feeling wise. He was, even after all bad things happen, still reluctant in disowning Anakin, in making him all bad, all Sith. That's why he choose to remember him as he was, insecure, proud and young, he preferred to remember him as a friend. Because that's what they were. From the start, friends and as a friend Obi Wan was never able to see the bad in Anakin, to make out what is hidden in the darkness.
In the time that passed in between Obi Wan, in the solitude where he called himself Ben, the name he had in the time before Jedi's took him in. He started to look into that which was in the darkness. Maybe they called it the dark side because it was a Jedi's blind spot, they just couldn't see what people on the other side are feeling, what are they planning and where are they going to. That was their down fall because they, Sith and his apprentice, were invisible until it was too late.
Even in his old age Obi Wan was still light-hearten person and he didn't like to dwell on the past. He called himself Ben, and of Anakin he thought as a long lost friend. It was fortunate that the side of the light was hard to look at too from the dark side. That way Ben could live by on Tatooine watching over young Luke without being discovered. He just had to stay away from the usage of the Force, which wasn't too hard for him.
Hard thing was to watch over Luke. To see the light within him, it shone so bright and strong, he was such a simple boy. It was hard because he was more like Obi Wan, light at heart, not corrupted by the harsh environment and the unforgiving Empire he was in, than like angry Anakin. It was hard because when Luke smiled at him not knowing who he was, smiling despite him being just an old hermit Ben no one talked to, Obi Wan couldn't but wonder what the world would look like if he was a braver man way back when. If he really did what Anakin thought of him. If he tried to act on that feeling Padme provoked in him. Feeling that he could be a strong man, a complete one, one which has an agenda of his own, a destiny of his own, not just the one the Jedi masters bestowed upon him.
Sadness. That's what this feels like. I wonder where this goes to.