In one of the great Hasidic works of philosophy, the Sfas Emes, it is suggested that this holiday does represent complete happiness because unlike other holidays, we can fulfill it completely. We should offer certain sacrifices. Our inability to perform these rituals taints our spirit for the holidays. However, on Chanukah, all we need to do is to light the candles and praise G-d. With this we have celebrated the holiday in its entirety, and our joy is complete.
Ideal happiness is deep-seated joy.
Everyone enjoys a good laugh, but a momentary laugh for a frivolous matter does not happiness make. Sometimes people experience a kind of superficial happiness for a period of time, only to be shattered a short time later by the slightest problem or challenge. The Torah often speaks of the joy of the heart. If the delight isn't as deep as one's heart, it is not true happiness. Chanukah may not seem like a big celebration.