Here is further evidence that there is no truly selfless act.
If and when you help a person in need, the only reason you do so is because it satisfies yourself, or makes you happy. If you did not gain something from the act, you would not do it.
For example, say you donate a can of soup to whatever charity that collects canned goods. That soup you gave hurts you financially a little bit, but not enough to make your life uncomfortable. Most people only give what they can bear to part with. So how is that admirable?
Why stop at the can of soup? If you really want to give and you really want to sacrifice, give half of the food in your house. Devote half of your grocery budget to the needy, and learn to live on rice and water. Who does that? Nobody I know.
Why? Because it hurts too much. It's outside the zone of comfortable sacrifice. And comfortable sacrifice isn't really sacrifice at all. Nobody gives so much that they make themselves unhappy.