Based on Bhagavad Gita Chapter 05, Text 21
Whenever Gita wisdom encourages us to perform any act of self-denial like fasting on certain holy days, the purpose is not self-torture, but self-fulfillment. Fulfilling our bodily requirements is necessary for survival, but not sufficient for satisfaction. Satisfaction comes only by the fulfillment of our spiritual necessity of a loving connection with the reservoir of all satisfaction, Krishna. However, as long as we are caught up in catering to bodily demands — as we normally are, we neglect our spiritual necessity and miss the lasting fulfillment available thereof.
The Gita recommends acts of self-denial to gently compel us to relish what we have been unnecessarily missing. Self-denial checks our bodily preoccupation and forces us to look at the spiritual level for fulfillment. If we look by the right process under the right guidance, then we get so much spiritual fulfillment that we don’t even miss the bodily needs that we normally consider indispensable.