Anakin didn't manage to let go, let go of loss and fear. He lost his battle against his own feelings, in my opinion he wasn't strong enough to let go. He was really weak in that department.
(a) The Dark Side is "unnatural" and it's very use unbalances the Force.
(b) The Force is balanced when good and evil are equal.
(c) Some other option (explain in your post, kplzthx).
Anakin didn't manage to let go, let go of loss and fear. He lost his battle against his own feelings, in my opinion he wasn't strong enough to let go. He was really weak in that department.