I have often asked myself, what's the purpose of life is. Frankly I don't know. But what I have experienced is that I love to take care of others. And I think this is a purpose of my life.
These others doesn't have to be people necessarily. For me it's also my dog. Taking care of my dog helps me too.
It gives me a sense of happiness, of importance, of responsibility and it keeps me fit for I have to walk him three times a day.