Joy comes through a feeling of achievement and pride in the self. The exodus from Egypt was G-d's doing. Therefore the two harvest festivals, which celebrate our hard earned harvest, Shavuos and Succos, are more joyous than Passover, which commemorates the exodus, because the joy of Shavuos and Succos is the joy of the labor of our own hands. The beginning of the salvation was our doing. To be sure, without G-d's help we could never have defeated the Greek Syrians, but we can take pride in the fact that we had a hand in our own redemption.
Ideal happiness involves the total mind or self.
Some activities are a pleasure for the palate but a pain for the stomach, good for the heart, but the legs take a beating. The author of the Shem Mishmuel points out that the three obligations of Chanukah engage our three faculties, guf, nefesh, and sechel, or body, soul, and mind. The obligation to thank G-d on Chanukah is an obligation of the body. The obligation to recite the Psalms of praise or Hallel is an obligation of the soul. The duty to light the candles represents the mind.