I'm not a parent yet, but I do agree to with this statement. Being a parent is one of the most ultimate selfless acts you can do (if you do it right) IMO.
To wake up every morning thinking about someone else OTHER than yourself is a major part of our growth experience in this world. Having another human being totally dependent on you (for a few years or a lifetime) is something that a text book can't teach you. Those moments will undoubtedly shape you as a person and help you have a greater understanding of love, patience, compassion, and unselfishness.
Oh shoot, I want to have a child now.