After Ed has to kill he has to deal with having killed and Roy has to deal with him. Divergent Future, Drama With Porn, faint spoiler ep 25.

Edward grabs Marcoh’s arm and says, “That stone – what can it heal, exactly?” The old man’s eyebrows rise to his forehead, and he looks like he already knows the answer when he goes, “Why do you ask, Edward?” There's no metallic footsteps so there’s no way Al’s close enough to hear them. “I’m sick,” he admits after another moment of deliberation.

Everyone is born with the ability to only see the colour of their soulmate's eyes. Only upon touching their soulmate, can people see the rest of the world's colours. Edward Elric will do whatever it takes to get his brother's body back and ensure he can have his happily ever after with his soulmate, even if it means never finding his own soulmate.