There can be purposes as "big things" and purposes that are not so big but nonetheless just as important. Every day when you touch someone's life it can make a difference to them, however small and insignificant it may seem. Simple things such as helping someone to cross the road, thanking someone for something they have done and showing your appreciation can make a difference to someone else's life.
I used to muse on my "purpose" - I don't have a long term partner and I don't have kids. In reality I lead a rather lonely, but nonetheless hectic but fulfilling life. So I suppose my "purpose" is to make the most of every new day.