I been thinking about the two scenes in the game. The Ranch Scene and The scene where Joel falls off the horse. On the brink of death.At the University before the Winter Scene.
I am just speculating. But maybe in this was Joel's chance to stop running from his past. And be reunited with Sarah in heaven. And when Ellie sewed Joel up which saved his life.
One could say by doing this. Essentially she winds up robbing Joel of that chance. By the time we, reach the UTAH Scene with the (giraffes). And Ellie hands Joel back the picture.
He replies: " I guess you, can't escape your past. Thank You. " . The words behind his "Thank You" Its not more like the kind of " Thank You. I am greatful to be a live." It actaully is the opposite.
Just like when Joel saves Ellie inside the hospital from dying. He robs Ellie of being the cure and also being reuntied with Riley. Because Ellie's response with her "Ok" at the end. Mirrors Joel's response when he says "Thank You"
I would like to hear what you, guys on this website thinks of this theory.