Will power, in my words, is the ability for someone to overcome the immediate want or temptation of something to increase value of some sort in the future. Practicing will power could be not buying something you want, getting up early and exercising, saving money, or even saying yes to help out a friend who needs help moving. You are avoiding the want of something now for something better in the future.
People are lame. We often do things the fastest and easiest way. We become hungry so we order a pizza. The grass is too long so we call up our local lawn care service. We get bored so we take a nap. The car is dirty so we get a carwash. We pay others to do the work. Or even worse we lie to them or ourselves. A friend needs help moving a couch so we convince ourselves that we are busy or aren't feeling well. All of these things are easier and are not exercising our will power. We are too lazy.
I try to practice will power everyday. I try to do something everyday that I don't want to do to. Sometimes that is avoiding beer, going for a walk when it is cold outside, skipping lunch with coworkers to save a few bucks, working out when I am tired, or skipping dessert. No matter what it is, I seem to feel stronger afterwards.
It seems it is similar when you say yes to someone else. Saying yes to help others is very fulfilling. Helping others is sometimes hard, but the returns almost always outweigh the effort. I don't think I know anyone that likes to move couches or beds for fun, but you always feel better afterwards. Or how about cooking a meal for your friends and family? It can be a lot of work, but it is always a great time and way less expensive than going out.