To a large extent, the will to do good for others is a natural outgrowth of spiritual development. The more connected you are to the infinite generosity of the universe, the more generous you feel. The more content you are inside, the more your cup runneth over and you think "How can I help?" instead of "What do I want?" The most revered spiritual figures in our history exemplify this: rather than bask in bliss under a tree or atop a mountain, they accepted the difficult mission of healing the wounded and waking up the sleepwalking masses.

But most of us don’t feel that full all the time; instead, we feel a lack that cries out to be filled. That's why spiritual teachings don't take any chances. They make it a virtual commandment to contribute to the greater good. Christians call it charity. Hindus call it seva, or service. Jews call it tzeddakah—acts of righteousness. One of the five pillars of Islam, right alongside formal prayer, is zakat, which obliges Muslims to tithe to the poor. Even Buddhism, with its emphasis on detachment, calls upon followers to dedicate their practices to all beings.

One reason for the universal call to generosity is that human beings need each other; the more we extend our circle of concern beyond ourselves, our immediate families and our tribes, the better off we all are. The other reason is that giving is good for the giver. There is a delicious irony in this: by serving selflessly, you serve yourself. When you think only about your own needs and wants, your mind constantly focuses on what you don't yet have, on problems to be solved and desires to be satisfied. This is, to a large extent, a recipe for discontent. By contrast, thinking about those in need expands the awareness beyond the ego, linking you to a larger whole. Quite often, it also triggers gratitude by putting your own small problems into perspective. That's what makes service a practice for spiritual growth as well as a natural result of that growth.

It's also good for your health. An impressive body of research suggests that those who regularly engage in acts of charity and service are healthier, happier and may even live longer than their more self-involved counterparts. A 30-year study at Cornell University, for example, found that those who did volunteer work were more satisfied and had a greater sense of purpose in life. Other studies have found: volunteers have lower stress levels, heightened immune response and sounder sleep; a selfless attitude makes happiness 2.4 times more likely, while a selfish attitude made unhappiness 9.5 times more likely; self-centered people run a greater risk of developing coronary artery disease; on average, seniors who volunteer outlive their compatriots who do not.

Just as in meditation or prayer, we get closer to our divine nature when we get our egos out of the way and serve a greater good. When we give ourselves away, we are doing what the Talmud calls mimicking God, and what Muslims call being worthy of the world that Allah created. "The stronger my feeling for taking care of others becomes, the more benefit I reap for myself," says the Dalai Lama. "Since overcoming negative tendencies and enhancing positive potential are the very essence of the spiritual path, the practice of developing altruism is really the greatest, most effective, and most compelling practice of all." So, this holiday season, in addition to or in lieu of the usual gift-giving, consider dipping into the noblest part of yourself instead of just your wallet. Service does not require Mother Teresa-like sacrifice. Nor does it have to be a somber duty. It can be as enjoyable as it is benevolent. Just look around you: there are thousands of worthy organizations begging for volunteers, numberless people whose lives would be made better by one generous gesture. If you can get your ego out of the way and perform a service in the spirit of innocent giving, you might find out why it's more blessed to give than to receive. The great Indian poet, Rabindranath Tagore, put it this way:

I slept and dreamt that life was joy,
I woke and saw that life was service,
I acted and behold!
Service was joy.