The small sufferings we willingly take on can be endured for the sake of those who have much greater sufferings. When we deny ourselves, we symbolically identify our plight with others who are also denied the good things of life, and our discomfort serves as a reminder to pray for them.
As often as you are able, deny yourself the best portion of a meal or a dessert and let someone else have it. Instead of reaching for the best part or the largest slice, take a less attractive piece and silently offer a prayer for those who never get the best part or may not be eating at all that day. Obviously, tell no one that you do this, so that you do not receive any praise or honor for it.— Tom Cowan in The Way of the Saints