It was a wise decision to separate these fish regardless of what you now perceive to be sullen behavior. These two species are incompatable as far as water parameters and temperature. Angels like a calm planted tank, and goldfish are pretty boisterous cold water creatures that can take a lot more water movement, (especially if we are referring to the straight-tailed varieties like comets). You might not have had trouble between them , but it would have happened.
I can't see your fish, so I don't know if the words "he does not want to do anything" refers to a refusal to eat or swim normally, or if you simply imagine he is less active because he is no longer being shoved around by some goldfish.
If he eats and generally seems interested in movement around the tank, if there are no blemishes, red ulcerous areas, white spots, ragged fins or cottony patches on the body, eyes, or mouth, I would stop worrying and stop trying to anthropomorphize this creature and simply enjoy him for what he is: an elegant, stealthy, predator of small food items. Stillness is one of his strategies.