We definitely do possess a desire for serving our own interests. However, at the same time, it would appear that we human beings have a genuine desire to serve the interests of other people as well. Human sympathy is a genuine desire. When we see a person in need, such as a blind person who wishes to cross the road, and we help him, we are not thinking of what we will be able to gain out of that action.
When a mother sees that her child is crying, the mother does not help the child in order to gain anything. Of course, we know that she would gain peace of mind or reward from God when she looks after her child, but in many if not most cases the intention behind her action is not to gain peace of mind or reward; she does it merely because she loves her child.
In my opinion, we human beings have two types of desires: desires which are oriented towards our own self-interest and desires which are oriented towards the interests of others. It is quite possible to do something to benefit others without even implicitly thinking about our own self-interest.