Is optimism and positive attitude counterproductive?

Many believe that it is important to avoid being negative and instead to see the good in bad situations. However, the Buddha said that good and bad are fabricated concepts that do not exist. An individual who has attained nirvana is neutral and does not experience emotions. Although a Bodhisattva is certainly not negative and pessimistic, they cannot be positive and optimistic either. Would seeing the bright side of things in life impede me from making spiritual progress?