The message that is sent to us by this act (mentioned in John 13:1-17) is that we should be humble. We should realize that, if Jesus was willing to humble himself by washing the feet of people who were clearly "lower" than he was, we should not feel that we are too good to treat other people with respect.
In our lives, it is very easy for us to feel arrogant. Our society encourages us to think of ourselves first and to feel that we are special. But when we reflect on this act, we should realize that we are not better than other people and we should not act as if we are. This might, for example, encourage us to do charity work that will help others or to pursue a career that is centered around helping others rather than around aggrandizing ourselves.