Zan Sayonara Zetsubou Sensei Bangaichi

Plunged into despair by the most seemingly-trivial occurrences, the ever-negative Nozomu Itoshiki continues to teach his class the unhappy ways of the world. After witnessing the dangers of vacillation as various demonstrations descend into little more than hesitancy and petty debate, the depressed teacher unwillingly falls prey to it himself. Throwing in the manipulative and pretentious nature of books, museums and society in general, it certainly seems like a carefree and happy life is impossible for the miserable Itoshiki. Source Anime-Planet